Musnad Ahmad 2:7

Harun ibn Ma'ruf narrated to us, he said: Ibn Wahb narrated to us, from 'Amr ibn al-Harith, from Abu al-Nadr, from Abu Salamah ibn 'Abd al-Rahman, from 'Abdullah ibn 'Umar, from Sa'd ibn Abi Waqqas, from the Messenger of Allah, may Allah bless him and grant him peace, that he wiped over the two leather socks. And 'Abdullah ibn 'Umar asked 'Umar about that, and he said: "Yes, if Sa'd narrates something to you from the Messenger of Allah, may Allah bless him and grant him peace, then do not ask anyone else about it."