(3) باب نَدْبِ مَنْ حَلَفَ يَمِينًا فَرَأَى غَيْرَهَا خَيْرًا مِنْهَا أَنْ يَأْتِيَ الَّذِي هُوَ خَيْرٌ وَيُكَفِّرَ عَنْ يَمِينِهِ
Tamim b. Tarafa reported:
A beggar came to 'Adi b. Hatim and he begged him to give him the price of a slave, or some portion of the price of the slave. He ('Adi) said: I have nothing to give you except my coat-of-mail and helmet. I will, however, write to my family to give that to you, but he did not agree to that. Thereupon 'Adi was enraged, and said: By Allah, I will not give you anything. The person (then) agreed to accept that, whereupon he said: By Allah, had I not heard Allah's Messenger (ﷺ) saying:" He who took an oath, but then found something more pious in the sight of Allah, he should (break the oath) and do that which is more pious," I would not have broken the oath (and thus paid you anything).
Reference: Sahih Muslim 1651 a
In-book reference: Book 27, Hadith 22
USC-MSA web (English) reference(deprecated numbering scheme): Book 15, Hadith 4056