The balanced approach of Islam is one of its most manifest characteristics. Naturally, then, it is also one of the most manifest characteristics of the nation who accepts the call to Islam. Allah says,
"Thus have We made of you a nation justly balanced, that you may be witnesses over the people and the Messenger a witness over yourselves" (al-Baqarah 143).
Therefore, one finds that Islam presents the moderate way in every aspect of life. Not only that, it also warns against heading towards either extreme: the extreme of too much zealousness and the extreme of too much nonchalance.
"Guide us to the straight way, the way of those upon whom You have bestowed Your grace, not those whose (portion) is wrath nor those who have gone astray" (al-Faatihah 6-7).
This balanced approach that distinguishes Islam from the other religions is the true justice and excellence. The words in the verse above, "a nation justly balanced (ummah wasat )," means "fair and most excellent."
This is its explanation in the Quran and Sunnah and as stated by the scholars of Quranic exegesis and Arabic language, to the point that such an interpretation has become agreed upon.
As for the explanation of that verse via the Quran itself, one should note the following:
(1) This is the interpretation that is most consistent with the remainder of the verse. The "balanced approach" is the reason why this nation has been assigned the role of witness against the other nations, "that you may be witnesses over the people." Testifying is only to be performed by just people as it is not acceptable from anyone except a just person. 
(2) Allah says,
"You are the best nation raised for mankind" (ali-Imraan 110).
Parts of the Quran explain each other. Since the Quran describes this nation as "the best," its description as "moderate and balanced" must necessarily follow because "moderate and balanced" in the Arabic language means "the best, most excellent," as shall be explained shortly, Allah willing. 
The Sunnah also clearly explains the "balanced approach of this nation" as meaning its just and excellent position. Abu Saeed al-Khudr  narrated that the Messenger of Allah (peace be upon him) said,
"On the Day of Resurrection, Noah will be brought and asked, 'Did you convey [the message]?' He will say, 'Yes, 0 Lord.' His nation will be asked, 'Was the message conveyed to you?' They answer, 'No warner came to us.' He [the Lord] will say [to Noah], 'Who are your witnesses?' He will answer, 'Muhammad and his nation.' Then you [that is, the followers of Muhammad] will be brought and will give witness." Then the Messenger of Allah (peace be upon him) read the verse, "Thus have We made of you a nation justly balanced,"-he stated, "[That is,] just,"- "that you may be witnesses over the people and the Messenger a witness over yourselves," 
This explanation [for the above verse] is also what the early scholars of Quranic exegesis stated, including ibn Abbaas,  Mujaahid,  Saeed ibn ]ubair,  Qataadah,  as well as others of the later Quranic commentators.  This usage is customary in the speech of the Arabs, that is, that "moderate, balanced" means just.
Al-Tabari, may Allah's mercy be upon him, said,
"The meaning of 'moderate, balanced in the speech of the Arab is 'best, choice.' One says [for example,] 'So and so is of the best lineage among his people' when he wants to raise a person's lineage." 
He also said,
"It also comes that 'the moderate' means 'the just,' and that is the meaning of 'best, choice,' because the best of the people are the just among them." 
This usage is also indicated by the words of Abu Bakr  (may Allah be pleased with him) when he described the Muhajireen (the Emigrants) on the day of Saqeefah of Banu Saadah  in the following manner, "They are the best (ausat) inhabitants of the Arabs." 
He stated that to express their excellence. Similarly, Zuhair ibn Abi Salmaa  said [roughly, in lines of poetry],
"They are just (wasat), the people being pleased with their judgment when a calamity strikes them on any night." The above is also expressed by the specialists in Arabic, such as al-Khaleel,  Qutrub  and others. 
It is a given that the word wasat means the [middle] portion [or position] between two ends.
However, there is no contradiction between wasat meaning "just" and wasat meaning the portion between two ends. This is because the middle portion centered between two ends is the place of moderation, avoiding the two extremes.
I opine that Allah describes them as being wasat (middle, balanced) due to their moderation and balance in religion. They are not from those who go to extremes in the religion, such as the extreme of the Christians who practiced monasticism and in what they said about the person of Jesus. Nor are they from those who are lackadaisical in the practice of their religion, such as the Jews who altered the Book of Allah, killed their prophets and lied in speaking about their Lord. Instead, they [the nation of Muhammad (peace be upon him)] are the people of balance and moderation in the religion.
Allah described them in that manner because the most beloved of matters to Allah are those that are balanced and just. 
In most cases, the just position is the median between two blameworthy positions. Hudhaifah ibn al-Yamaan said,
"Beware of Allah, 0 Quranic reciters [that is, religious scholars]. Follow the path of those before you. Then you will be the best of leaders. But if you go right or left, then you will go far astray." 
Umar ibn Abdul Azeez  wrote to one of his workers, saying, after advising him to follow the path of the early predecessors,
"There is no room to fall short of them and there is no room to go beyond them. Some people shortened the matter and fell short. Some people went above them and therefore went to extremes. They [the pious predecessors] were between that [those two extremes] upon a straight guidance." 
This is something that is established in the statements of the people of knowledge. [For example,] ibn al-Qayyim  wrote,
Allah does not make any command except that Satan has two incitements [toward it], either to negligence and neglect or to excess and exaggeration. The religion of Allah is in a middle position between being aloof from it and exaggerating in it. It is like a valley between two mountains, guidance between two astray positions and the middle, just position between two blameworthy positions. In the same way that one who is aloof from a matter loses that matter, the one who exaggerates also loses that matter. The first by his not meeting the minimum requirements and the second by going beyond the limits. 
The statement, "Virtue is being in a moderate position between two vices," is mistaken in that it makes human criteria the judge of vices and virtues. This is not correct due to the following:
(1) The determination of what is virtue and what is vice rests with Allah. And it is the result of what is just and it is not a matter that is left to the whims of humans.
(2) The real moderation is a divine decree,
"We have made you a balanced, moderate nation" (al-Baqarah 143).
(3) Delineating what is a middle position is difficult. Those who say that moderation is the standard for virtue admit this fact.
Aristotle  stated,
"To discover the moderate, middle position of everything is very difficult." 
Al-Ghazaali  stated about knowing the middle position,
"It is one of the most complicated and difficult of matters." 
(4) The delineating of the middle position is actually a relative matter [when it comes to humans] that changes with different people. For that reason, ibn Seena  said,
"The middle of something is not the exact middle but it is the middle with respect to us [and our perspective]." 
This makes it clear that moderation cannot be a human criterion for virtues. Instead, it is a distinguishing characteristic by which this religion of Islam and its law are distinguished. It is the religion and its adherents who are truly the people who are free of deviation, with respect to both extremism and negligence.
The shapes and manifestations of this balance and moderation are many in the religion as it is inclusive of all aspects of life. Every facet of the aspects of Islam has come in a manner that is consistent with justice. Here I shall only mention one example, as numerous other examples will be mentioned throughout this research since each phenomenon of extremism will be exposed by presenting the just and moderate correct view.
With respect to the material world, historically people have taken to extreme approaches. One group strayed and saw wealth as the main goal and ultimate aim. Those are the Jews whom Allah describes with the words,
"And verily, you will find them the greediest of mankind for life" (al-Baqarah 96).
Another group, the Christians, also strayed and they denied themselves their rights of life and they invented monasticism. [Allah says about them],
"But the monasticism which they invented for themselves, We did not prescribe for them. (We commanded) only the seeking of Allah's Pleasure; but that they did not tend to as they should have" (al-Hadeed 27).
In the face of those twO divergent paths, Islam came with the true justice and it gave everything its due right. Allah says,
"But seek with the (wealth) which Allah has bestowed on you, the home of the Hereafter, yet do not forget your portion in this world" (al-Qasas 77). 
Allah also says,
"Say: Who has forbidden the beautiful (gifts) of Allah that He has produced for His servants and the things clean and pure (which He has provided) for sustenance?" (al-Araaf 32).
Allah has also prohibited one from going to the extreme in loving wealth by saying,
"Know that the life of this world is but play and amusement, pomp and mutual boasting and multiplying (in rivalry) among yourselves, riches and children. Here is a similitude: How rain and the growth which it brings forth delight (the hearts of) the tillers; yet soon it withers; you will see it grow yellow; then it becomes dry and crumbles away, but in the Hereafter is a penalty severe as well as forgiveness from God and His Good Pleasure. And what is the life of this world, but goods and chattels of deception?" (al-Hadeed 20).
The Messenger of Allah (peace be upon him) also forbade being very strict upon oneself and intimidating oneself as the Christians did. He said,
"Do not be very strict on yourselves for then Allah will be strict upon you. Verily, a people were strict upon themselves so Allah was strict upon them. It is the remnants of those people in the hermitages and monasteries. [Then he quoted the verse,] 'But the monasticism which they invented for themselves, We did not prescribe for them."' 
This shows that the foundation of the religion itself is the antithesis of extremism. It is the religion of moderation and justice.
This is its distinguishing feature among all of the ways of life.
1) [Wasat can literally mean "middle." In the following passage, the author is trying to demonstrate and stress that its meaning is not only "middle," but being "middle" or "balanced" implies, linguistically and logically, that it is the just and best nation.-JZ]
2) Cf., what Ibn Hajar quoted from ibn Bataal, al-Fath, vol. 13, p. 613; also see Muhammad Abu Shaqrah, Tanweer al-Afhaam, p. 54.
3) See al-Shanqeeti, Adhwaa al-Bayaan, vol. 1, p. 87.
4) He was Saad ibn Maalik ibn Sanaan al-Khudri al-Ansaari al-Khazraji. He was among those who constantly stayed in the company of the Messenger of Allah (peace be upon him). 1170 hadith have been narrated on his authority. He participated in twelve of the battles of the Prophet (peace be upon him). He died in 'Madinah in the year 74 A.H. Cf., Siyar Alaam al-Nubalaa, vol. 3, p. 168; Tahdheeb al-Tahdheeb, vol. 3, p. 479; al-Alaam, vol. 3, f.87.
5) Recorded by al-Bukhari, al-Tirmidhi and Ahmad.
6) He was Abdullah ibn Abbaas ibn Abdul Mutalib, the cousin of the Messenger of Allah (peace be upon him). He was the great scholar of Islam and the interpreter of the Quran. He was born in Makkah. He was from those who narrated a large number of hadith; 1660 hadith have been narrated on his authority. He was at the Battle of the Camel as well as the Battle of Sifeen on the side of Ali. He lost his sight at the end of his life. He lived in Taif. He died in 68 A.H. Cf., Siyar Alaam al-Nubalaa, vol. 3, p. 331; Tahdheeb al-Tahdheeb, vol. 5, p. 276; and al-Alaam, vol. 4, p. 95.
7) Mujaahid was Abu al-Hajaaj Mujaahid ibn Jabr al-Makki, a freed slave of the tribe of Makhzoom. He was from the generation of the Followers and was a commentator on the Quran. Al-Dhahabi said, "He was the 'Shaikh' of the Qur'anic reciters and commentators. He learned Quranic commentary from ibn Abbas." He died in 104 A.H. Cf., Siyar Alaam al-Nubalaa, vol. 4, p. 449; Tahdheeb al-Tahdheeb, vol. 10, p. 42; al-Alaam, vol. 5, p. 278.
8) He was Saeedibn Jubair ibn Hishaam, through clientage from the tribe of al-Asadi, originally from Kufah, from the generation of the Followers. He was an Imam, reciter of the Quran and Qur'anic commentator. He learned from ibn Abbas and ibn Umar. Al-Hajaaj captured him and killed him in 95 A.H. Cf., Siyar Alaam al-Nubalaa, vol. 4, p. 21; Tahdheeb al-Tahdheeb, vol. 4, p.
11; al-Alaam, vol. 3, p. 93.
9) He was Abu al-Khataab Qataadah ibn Duaamah al-Sadoosi, a Qur'anic commentator and memorizer (haafidh). He was a leader in Qur'anic commentary, hadith and Arabic vocabulary. He died in Waasit during the pestilence of 118 A.H. Cf., Siyar Alaam al-Nubalaa, vol. 5, p. 269; Tahdheeb al-Tahdheeb, vol. 8, p. 351; al-Alaam, vol. 5, p. 189.
10) See the following Qur'anic commentaries: al-Tabari, Jaami al-Bayaan, vol. 2, pp. 7-8; al-Qurtubi, Al-Jaami li-Ahkaam al-Quraan, vol. 2, pp. 153-154; ibn Katheer, Tafseer al-Quraan al-Adheem, vol. 1, p. 190; al-Raazi, al-Tafseer al-Kabeer, vol. 4, p. 97; al-Shaukaani, Fath al-Qadeer, vol. 1, p. 150.
11) Al-Tabari, Jaami al-Bayaan, vol. 2, p. 7.
13) He was the rightly guided caliph Abu Bakr Abdullah ibn Abi Qahaafah Uthmaan Aamir ibn Kaab al-Taimiy al-Qurashi, the first caliph, the first man to believe in the Messenger of Allah (peace be upon him). He was born in Makkah and grew up in a rich, respected family. He was knowledgeable of the lineage and history of the Arabs. He was nicknamed "the scholar of Quraish." 142 hadith have been narrated on his authority. He died in 13 A.H. Cf., Ibn Hajar, al-Isaabah, vol. 6, p. 155; al-Alaam, vol. 4, f.12.
14) The Saqeefah of the Tribe of Saadah was a place belonging to a people of the Khazraj tribe, the clan of Saadah ibn Kaab ibn al-Khazraj, the grandfather, living in pre-Islamic times, of many of the Companions, including Saad ibn Ubaadah. Cf., Ibn Hazm, Jamhurah Ansaab al-Arab, p. 365; ibn Qudaamah, al-Istibsaar, p. 93. [It is the place in which many of the Companions gathered immediately following the death of the Prophet (peace be upon him).-JZ]
15) Part of a lengthy hadith in Sahih al-Bukhari dealing with the death of the Prophet (peace be upon him).
16) He was Zuhair ibn Abi Salma Rabeeah ibn Ribaah al-Mazani, from the poets of pre-Islamic times. He was born in the outskirts of Madinah thirteen years before the Hijrah. He has a collection of poetry that has been published. Cf., al-Alaam, vol. 3, p. 52. The Quranic commentators have attributed the line quoted above to him but I did not find it in his published collection.
17) He was al-Khaleel ibn Ahmad ibn Amr ibn Tameem al-Faraaheedi al-Azdi, one of the leading scholars of language and literature. He was considered one of the most intelligent of the Arabs. He laid down the principles of prosody. He was born in Basrah in 100 A.H. and died in 170 A. H. Cf., Siyar Alaam al-Nubalaa, vol. 7, p. 429; al-Alaam, vol. 2, p. 413.
18) He was Muhammad ibn al-Mustaneer ibn Ahmad. He was a grammarian and scholar of literature and language. He was from the "clients" of Basrah. He was the first to put the three diacritical points in the language. He was given the nickname Qutrub by [the famed grammarian] Seebawaih. He died in 206 A.H. Cf., al-Alaam, vol. 7, p. 95.
19) Cf., al-Raazi, al-Tafseer al-Kabeer, vol. 4, p. 97.
20) Al-Tabari, Jaami al-Bayaan, vol. 2, p. 6.
21) Recorded by al-Bukhari, Abdullah ibn Ahmad in al-Sunnah and others.
22) He was the caliph Umar ibn Abdul Azeez ibn Marwaan al-Umawwi al-Qurashi, the pious caliph known as "the fifth of the rightly guided caliphs." He was born and raised in Madinah. He was a governor for alWaleed and then worked for Sulaimaan in al-Shaam. He became the caliph after Sulaimaan. Numerous people, including ibn al-Jauzi, have written works about him. He died in 101 A.H. Cf., Siyar Alaam al-Nubalaa, vol. 5, p.114; Tahdheeb al-Tahdheeb, vol. 7, p. 475; al-Alaam, vol. 5, p. 50.
23) Recorded by Abu Dawood. It is a lengthy quote but only the relevant portion was quoted here. The first two sentences have been explained in al-Aun al-Mabood as meaning, "The pious predecessors would refrain themselves from revealing what was not necessary to be revealed of the matters of the religion, withholding without going beyond. Similarly, they would reveal what was needed of the religion without going beyond." Al-Adheemabaadi, Aun al-Mabood, vol. 12, pp. 369-370.
24) He was Muhammad ibn Abu Bakr ibn Ayyoob al-Damashqi, one of the well-grounded scholars. He was born in 691 A.H. in Damascus. He was a student of ibn Taimiyyah. He was a reformer. He wrote numerous beneficial works, including al-Sawaaiq al-Mursalah, Ilaam al-Muwaqieen and others. Numerous people have written biographies about him, including Abdul Adheem Sharf al-Deen and Bakr Abu Zaid. Cf., al-Alaam, vol. 6, p.56.
25) Ibn al-Qayyim, Madaarij al-Saalikeen, vol. 2, p. 496. Also see ibn al-Qayyim, al-Fawaaid, pp. 139-140; al-Shanqeeti, Adhwaa al-Bayaan, vol. 1, p. 494.
26) Aristotle was the most famous of the ancient Greek philosophers, nicknamed "the prince of philosophy." He was born in 384 B.C. and died in 322 B.C. See Muhammad Fareed Wajdi, Daairah Maarif al-Qarn al-Ishreen, vol. 1, p. 164.
27) Al-Akhlaaq, Book 5, Chapter 5, Section 14, quoted from Dr. Ahmad Ibraaheem, Al-Fadhaail al-Khuluqiyyah, p. 273.
28) He was Abu Haamid Muhammad ibn Muhammad ibn Muhammad al-Ghazaali, a legal theorist, jurist, philosopher and Sufi. He produced about two hundred writings. He was born in 450 A.H. He traveled in search of knowledge and to teach. He has many famous books, including Ihyaa Uloom al-Deen, al-Mustasfa and others. See al-Alaam, vol. 7, p. 22.
29) Meezan al-Amal, p. 273. 4
30) He was al-Husain ibn Abdullah [known in the West as Avicennaj, the philosopher. He wrote works on medicine, logic and nature. He was originally from Balkh. He wrote numerous works but had a number of discrepancies - that cannot be explained away-when it came to matters of belief. Ibn Taimiyyah discussed a number of those issues in his great work, Dar al-Taaradh al-Aql wa al-Naql. He died in 428 A.H. Cf., Siyar Alaam al-Nubalaa, vol. 17, p. 531 and al-Alaam, vol. 2, p. 241.
31) Ilm al-Akhlaaq, p. 245. See Ahmad Abdul Rahmaan Ibraaheem, al-Fadhaail al-Akhlaaqiyyah, p. 272. In that work is an excellent critique of the view that moderation is the sole criterion for virtue.
32) Cf., the commentary on this verse in ibn Katheer, Tafseer al-Quran al-Adheem, vol. 3, p. 399.
33) Recorded by Abu Dawood and Abu Yala. Its chain contains Saeed ibn Abdil Rahmaan ibn Abi al-Umyaa. He was considered trustworthy by ibn Hibbaan. AI-Dhahabi states in al-Kaashif, "He was trusted." Ibn Hajar stated in al-Taqreeb, "Acceptable [if he has supporting evidence]." Al-Haithami stated, "Recorded by Abu Yala and its narrators are from the Sahih collections, save for Saeed ibn Abdul Rahmaan ibn Abi al-Umyaa, and he is trustworthy" (Majma al-Zawaaid, vol. 6, p. 256). Cf., ibn Katheer, Tafseer al-Quran al-Adheem, vol. 4, p. 316; al-Suyooti, al-Durr al-Manthoor, vol. 4, p. 178; aI-Hindi, Kanz al-Ummaal, #5346; the editor of Musnad Abi Yala said (vol. 6, p. 365), "Its chain is hasan."