If he, sallallaahu ‘alayhi wa sallam, was invited, and a person followed him who was not invited, he would ask permission from the host:

“A man from the Ansaar called Abu Shu’ayb had a slave who was a butcher. He saw the Prophet of Allah, sallallaahu ‘alayhi wa sallam, and knew from his face that he was hungry. He told the slave, ‘Woe to you, prepare some food for five people, for I want to invite the Messenger of Allah in a party of five.’ He invited the Messenger of Allah, sallallaahu ‘alayhi wa sallam, in a group of five people, and a man followed them. When he reached the door, he, sallallaahu ‘alayhi wa sallam, said: “This man has followed us. If you like, you can give him permission, and if you like, he will return.” He said: ‘Rather I give him permission, O Messenger of Allah.’”