Sahih Bukhari | Volume 3 | Hadith Number 636

Narrated by Abu Mas'ud
There was an Ansari man called Abu Shu'aib who had a slave butcher. Abu Shu'aib said to him, "Prepare a meal sufficient for five persons so that I might invite the Prophet besides other four persons." Abu Shu'aib had seen the signs of hunger on the face of the Prophet and so he invited him. Another man who was not invited, followed the Prophet. The Prophet said to Abu Shu'aib, "This man has followed us. Do you allow him to share the meal?" Abu Shu'aib said, "Yes."