Sahih Bukhari, Chapter: Sales and Trade

An Ansari man, called Abu Shuaib, came and told his butcher slave, "Prepare meals sufficient for five persons, for I want to invite the Prophet along with four other persons as I saw signs of hunger on his face." Abu Shuaib invited them and another person came along with them. The Prophet said (to Abu Shuaib), This man followed us, so if you allow him, he will join us, and if you want him to return, he will go back." Abu Shuaib said, "No, I have allowed him (i.e. he, too, is welcomed to the meal)."