Musnad Abu Ya'la al-Mawsili 154:35

Mujahid ibn Musa narrated to us, Hajjaj narrated to us, he said: Ibn Jurayj said: 'Amr ibn Yahya ibn 'Umarah informed me that Sa'id ibn Yasar, Abu al-Hubab, informed him that he heard 'Abdullah ibn 'Umar saying: "I saw the Messenger of Allah (may Allah bless him and grant him peace) praying while he was heading toward Tabuk."