Musnad Ahmad 175:9

Hajjaj narrated to us, Layth narrated to us, he said: Uqayl narrated to me, from Ibn Shihab, from the son of Ka’b ibn Malik, and Ka’b ibn Malik—one of the three who were forgiven—that Ka’b ibn Malik said: "When the Messenger of Allah, peace and blessings of Allah be upon him, would arrive from a journey, he would begin with the mosque and pray two rak'ahs in it. Then he would greet, and sit in his place of prayer, and the people would come to him and greet him."