Sahih Muslim Book 23, Hadith Number 5061.

Chapter : Permissibility of a person’s taking anyone along with him where the host is very intimate with the guest.

Anas b. Malik reported: Abu Talha ordered Umm Sulaim to prepare a meal specially for Allah’s Apostle (may peace be upon him). He then sent me to him (to the Holy Prophet) ; the rest of the hadith is the same (but there is a slight variation of wording): “Allah’s Messenger (may peace be upon him) placed his hand and mentioned the name of Allah upon that, and then said: Admit ten men. He (Abu Talha) admitted them and they got in. He (the Holy Prophet) said: Eat while mentioning the name of Allah upon it (the meal). They ate until eighty persons had taken the food. Then Allah’s Apostle (may peace be upon him) had his meal and so the members of the household, and still they left some food.”