Musannaf Ibn Abi Shayba 19:711

Abu Bakr narrated to us, he said: Muhammad ibn al-Hasan narrated to us, from Muhammad ibn Sulaym, from Abu Hilal, from Najih, who said: The Messenger of Allah (may Allah bless him and grant him peace) stoned, and Abu Bakr and Umar stoned, and their command is a Sunnah.