Sahih Muslim 1651 a
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).
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا جَرِيرٌ، عَنْ عَبْدِ الْعَزِيزِ، - يَعْنِي ابْنَ رُفَيْعٍ - عَنْ تَمِيمِ بْنِ طَرَفَةَ، قَالَ جَاءَ سَائِلٌ إِلَى عَدِيِّ بْنِ حَاتِمٍ فَسَأَلَهُ نَفَقَةً فِي ثَمَنِ خَادِمٍ أَوْ فِي بَعْضِ ثَمَنِ خَادِمٍ ‏.‏ فَقَالَ لَيْسَ عِنْدِي مَا أُعْطِيكَ إِلاَّ دِرْعِي وَمِغْفَرِي فَأَكْتُبُ إِلَى أَهْلِي أَنْ يُعْطُوكَهَا ‏.‏ قَالَ فَلَمْ يَرْضَ فَغَضِبَ عَدِيٌّ فَقَالَ أَمَا وَاللَّهِ لاَ أُعْطِيكَ شَيْئًا ثُمَّ إِنَّ الرَّجُلَ رَضِيَ فَقَالَ أَمَا وَاللَّهِ لَوْلاَ أَنِّي سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ ‏
"‏ مَنْ حَلَفَ عَلَى يَمِينٍ ثُمَّ رَأَى أَتْقَى لِلَّهِ مِنْهَا فَلْيَأْتِ التَّقْوَى ‏"‏ ‏.‏ مَا حَنَّثْتُ يَمِينِي ‏.‏