Musnad Ahmad 30:694

'Abd al-Razzaq narrated to us, Ma'mar informed us, from Muhammad ibn Ziyad, I heard Abu Hurayrah saying: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When one of you puts on sandals, let him begin with the right, and when he takes them off, let him begin with the left. And let him take them both off together, and let him put them both on together."