Muwatta Imam Malik (Riwayat Ibn al-Qasim)

It is narrated from Sayyiduna Mihjan (may Allah be pleased with him) that he was sitting with the Messenger of Allah (peace and blessings of Allah be upon him) in a gathering. Then the call to prayer was given, so the Messenger of Allah (peace and blessings of Allah be upon him) stood up and led the prayer. Then he returned, and Sayyiduna Mihjan (may Allah be pleased with him) was still present in his gathering. The Messenger of Allah (peace and blessings of Allah be upon him) asked him: "Why did you not pray with the people? Are you not a Muslim man?" Mihjan said: "Yes, O Messenger of Allah! I am a Muslim, but I had already performed this prayer at home." So the Messenger of Allah (peace and blessings of Allah be upon him) said to him: "If you have already prayed and (then) come (to the mosque), then pray with the people (again)."