Abu Mas‘ūd Al-Badri (may Allah be pleased with him) reported that a man invited the Prophet (may Allah's peace and blessings be upon him) to a meal that he prepared for him and four others. A man followed them, and when he arrived at the door, the Prophet (may Allah's peace and blessings be upon him) said (to the host): "This man followed us. If you wish, allow him to come in, and if you wish, he will go back." He (the host) said: "O Messenger of Allah, I admit him." Authentic hadith - Narrated by Bukhari & Muslim