Musnad Abu Ya'la al-Mawsili 147:7

Mu'adh ibn Shu'bah narrated to us, Dawud ibn al-Zibriqan narrated to us, from Abu al-Haytham, from Ibrahim al-Taymi, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "When food is brought near to one of you while he is wearing sandals on his feet, let him remove his sandals, for it is more restful for the feet and it is from the Sunnah."