Musnad Ahmad 175:10

'Abd al-Razzaq narrated to us, he said: Ma'mar narrated to us, from al-Zuhri, from 'Abd al-Rahman ibn Ka'b ibn Malik, from his father: "The Prophet, peace and blessings of Allah be upon him, arrived from the expedition of Tabuk in the forenoon. He prayed two rak'ahs in the mosque, and whenever he returned from a journey, he would do that."