Musnad Ahmad 457:23

Ibn Numayr narrated to us, al-A‘mash narrated to us, from Shaqiq, from Abu Mas‘ud, from a man of the Ansar whose kunya was Abu Shu‘ayb, who said: I came to the Messenger of Allah, may Allah bless him and grant him peace, and I recognized hunger in his face. So I went to a servant of mine who was a butcher, and I ordered him to prepare food for us for five men. He said: Then I invited the Messenger of Allah, may Allah bless him and grant him peace, as the fifth of five. A man followed them, and when the Messenger of Allah, may Allah bless him and grant him peace, reached the door, he said: "This man has followed us; if you wish, you may give him permission, otherwise he will return." So he gave him permission.