Sahih Muslim 2054 b
Abu Huraira reported that a guest spent the night with a person from the Ansar who had nothing with him but food (sufficient) for his own self and his children. He said to his wife:
(Lull) the children to sleep, and put out the lamp, and serve the guest with what you have with you. It was on this occasion that this verse was revealed:" Those who prefer the needy to their own selves in spite of the fact that they are themselves in pressing need" (Lix. 9).
حَدَّثَنَا أَبُو كُرَيْبٍ، مُحَمَّدُ بْنُ الْعَلاَءِ حَدَّثَنَا وَكِيعٌ، عَنْ فُضَيْلِ بْنِ غَزْوَانَ، عَنْ أَبِي،
 حَازِمٍ عَنْ أَبِي هُرَيْرَةَ، ‏.‏ أَنَّ رَجُلاً، مِنَ الأَنْصَارِ بَاتَ بِهِ ضَيْفٌ فَلَمْ يَكُنْ عِنْدَهُ إِلاَّ قُوتُهُ وَقُوتُ
 صِبْيَانِهِ فَقَالَ لاِمْرَأَتِهِ نَوِّمِي الصِّبْيَةَ وَأَطْفِئِي السِّرَاجَ وَقَرِّبِي لِلضَّيْفِ مَا عِنْدَكِ - قَالَ -
 فَنَزَلَتْ هَذِهِ الآيَةُ ‏{‏ وَيُؤْثِرُونَ عَلَى أَنْفُسِهِمْ وَلَوْ كَانَ بِهِمْ خَصَاصَةٌ‏}‏