Jami` at-Tirmidhi 1099

Abu Mas'ud narrated:"A man named Abu Shu'aib came to a slave of his, who was a butcher, and said: 'Prepare some food for me that will be sufficient for five, for I have seen hunger in the face of the Messenger of Allah.' So he prepared some food. Then he sent a message to the Prophet inviting him and those who were sitting with him. When the Prophet stood, he was followed by a man who was not with them when they were invited. When the Messenger of Allah arrive at the door he said to the owner of the house: 'A man who was not with us when you invited us followed us, if you permit him, he will enter.'" He said: We have permitted him, let him enter