Musnad Abu Ya'la al-Mawsili 7:8

Yahya ibn Abd al-Hamid al-Hummani narrated to us, Sharik narrated to us, from Asim ibn Ubayd Allah, from Abdullah ibn Amir ibn Rabi'ah, who said: I saw Abd al-Rahman ibn Awf circumambulating the House (the Kaaba) while he was wearing two leather socks (khuffayn). Umar said to him, "I do not know which of the two is more astonishing: your circumambulating around the House, or your circumambulating in your two leather socks." He replied, "I did this during the time of one who was better than you, the Messenger of Allah, may Allah bless him and grant him peace, and he did not criticize me for that."