Musnad Ahmad 30:2873

Ishaq narrated to us, Malik narrated to us, from Abu al-Zinad, from al-A’raj, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When one of you puts on his sandals, let him begin with the right, and when he takes them off, let him begin with the left. Let the right be the first of them to be put on, and the last of them to be taken off."