Sahih Muslim 5360

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)