Is not fulfilling a promise considered a sin if one is unable to fulfill it due to a quarrel that prevented it?

The promise to buy something for your friend's mother is recommended (mustahabb), and fulfilling it is not obligatory (wajib), but rather it is among the noble virtues. Breaking a promise is not characteristic of people of chivalry. Al-Shafi'i, Abu Hanifa, and the majority of scholars held the view that fulfilling a promise is recommended, while a group of scholars held that it is obligatory. The Malikis held that if the promise is linked to a reason, then fulfilling it becomes obligatory; but if it is an absolute promise, then it is not obligatory.