Sahih Muslim Book 23, Hadith Number 5100.

Chapter : Showing honour to the guest and the merit of making of sacrifice for him.

Abu Huraira reported that a person came to Allah’s Messenger (may peace be upon him) and said: I am hard pressed by hunger. He sent (message) to one of his wives (to procure food for him), but she said: By Him Who has sent you with Truth, there is nothing with me (to serve him) but only water. He (the Holy Prophet) then sent the (same) message to another, and she gave the same reply, until all of them gave the same reply: By Him Who has sent thee with the Truth, there is nothing with me but only water, whereupon he (the Holy Prophet) said: Allah would show mercy to him who will entertain this guest tonight. A person from the Ansar stood up and said: Messenger of Allah, I (am ready to entertain). He took him to his house and said to his wife: Is there anything with you (to serve the guest)? She said: No, but only a subsistence for our children. He said: Distract their attention with something, and when the guest enters extinguish the lamp and give him the impression that we are eating. So they sat down and the guest had his meal. When it was morning he went to Allah’s Apostle (may peace be upon him) who said: Allah was well pleased with what you both did for your guest this night.