739/1 - Abu Mas‘ūd al-Badri (may Allah be pleased with him) reported: A man prepared some food especially for the Prophet (may Allah’s peace and blessings be upon him) and invited him along with four others. But a man accompanied him. When they arrived at the door, the Messenger said to the host: “This person has followed us. You may allow him, if you wish, and if you wish, he will return.” He said: “O Messenger of Allah, I allow him.” [Narrated by Al-Bukhāri and Muslim]
1) It is permissible for a person to invite specific number of invitees. There is nothing wrong with that.
2) There is no blame upon the host if he does not give permission to a person who accompanied the invitee; and if he asks him to go back, he should comply. These are the manners taught in the Qur’an: {And if it is said to you, “Go back,” then go back.} However, it is noble and kind of the host to give permission to the one who has come without invitation and not ask him to go back.
3) Hospitality is legitimate and its desirability is affirmed.