Praise be to Allaah.
Undoubtedly keeping promises and keeping one's word are attributes of the believers, and breaking promises is one of the attributes of the hypocrites, as was narrated from 'Abd-Allaah ibn 'Amr (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: "There are four (characteristics), whoever has them is a hypocrite, and whoever has one of the four has a characteristic of hypocrisy unless he gives it up: when he speaks, he lies; when he makes a promise he breaks it; what he makes a pledge he betrays it; and when he disputes he resorts to foul language." Narrated by al-Bukhaari, 2327; Muslim, 58.
The believer who makes promises to people and breaks his promise may have an excuse or he may not. If he has an excuse then there is no sin on him, but if he does not have an excuse then he is a sinner.
There is no text - as far as we know - that makes any exception regarding the prohibition of breaking promises, but it may be that promises are broken in situations where the believer is excused. For example:
A - Forgetting
Allaah has forgiven us for forgetfulness whereby obligatory actions are omitted or haraam actions are committed. Allaah says (interpretation of the meaning):
"Our Lord! Punish us not if we forget or fall into error"
[al-Baqarah 2:286]
And Allaah has said: "Yes." - Narrated by Muslim, 125, from the hadeeth of Abu Hurayrah. According to another version, He said: "I will do that." Narrated by Muslim, 126, from the hadeeth of Ibn 'Abbaas.
Whoever makes a promise to someone then forgets the promise or forgets to do it at the time stated, there is no sin on him.
B - Being forced to break one's promise.
Being forced is one of the impediments that make it permissible for a Muslim to break his promise, such as one who is detained or is prevented from fulfilling his promise, or who is threatened with a painful punishment.
It was narrated from Ibn 'Abbaas that the Prophet (peace and blessings of Allaah be upon him) said: "Allaah has forgiven my ummah for their mistakes, what they forget and what they are forced to do."
Narrated by Ibn Maajah, 2045, and this hadeeth has many corroborating reports; classed as saheeh by Shaykh al-Albaani in Saheeh al-Jaami', 1836.
C - A promise to do something haraam or not to do something obligatory.
Whoever promises someone that he will do something haraam for him, or that he will not do something that is obligatory, it is not permissible for him to fulfil that promise.
This may be supported by the hadeeth of 'Aa'ishah - which is also known as the hadeeth of Bareerah - which is narrated in al-Saheehayn. 'Aa'ishah (may Allaah be pleased with her) had promised Bareerah's former masters [?} that the wala' of Bareerah [the right to inherit from her when she died - which is the right of the one who sets a slave free - Translator] would belong to them even though 'Aa'ishah (may Allaah be pleased with her) was the one who was going to set Bareerah free. But she did not keep this promise because they had gone against the sharee'ah and they knew that the right of wala' belonged to the one who set the slave free, so how could 'Aa'ishah set her free and then the wala' of Bareerah belong to them?
Al-Shaafa'i said:
When news of that reached them, the one who had stipulated a condition that was contrary to the ruling of Allaah and His Messenger was a sinner, and there are hudood punishments and discipline for the sinner. One of the ways in which the sinners are disciplined is that their conditions are rendered null and void so as to deter them and others from doing likewise. This is one of the best forms of discipline.
Ikhtilaaf al-Hadeeth, p. 165.
D - If something unforeseen happens to the one who made the promise, such as sickness, the death of a relative or breakdown of his means of transportation, etc.
There are many excuses, which all come under the heading of the verse (interpretation of the meaning):
"Allaah burdens not a person beyond his scope"
[al-Baqarah 2:286]
And Allaah knows best.
