Musnad Abu Ya'la al-Mawsili 153:143

Abu Khaythama narrated to us, Abd al-Samad narrated to us, Hammam narrated to us, Matar narrated to us, from Salim, from his father, who said: I traveled with the Prophet, may Allah bless him and grant him peace, and with Umar, and they would not exceed two rak'ahs. We were astray, then Allah guided us, and by him we follow.