Maliks Muwatta Book 48, Hadith Number 16.

Section : Wearing Sandals.

Yahya related to me from Malik from his paternal uncle Abu Suhayl ibn Malik from his father that Kab al-Ahbar said to a man who took off his sandals, “Why have you taken off your sandals? Perhaps you have interpreted this ayat, ‘Remove your sandals. You are in the pure valley of Tuwa?’ (Sura 20 ayat 12) Do you know what the sandals of Musa were?”

Malik (the father of Abu Suhayl) said, “I do not know what the man answered.” Kab said, “They were made from the skin of a dead donkey.”