Musnad Ahmad 2:75

Hashim narrated to us, he said: Ali bin Zaid informed us, from Yusuf bin Mahran, from Ibn Abbas, who said: Umar bin al-Khattab delivered a sermon—and Hashim said once: He delivered a sermon to us—so he praised Allah and extolled Him, then he mentioned the stoning (rajm), and said: Do not be deceived regarding it, for it is a prescribed punishment (hadd) from the prescribed punishments of Allah. Beware, for the Messenger of Allah (peace and blessings of Allah be upon him) did stone, and we stoned after him. And were it not that people would say: "Umar has added to the Book of Allah, the Mighty and Majestic, that which is not from it," I would have written it in a corner of the Mushaf. Umar bin al-Khattab testified—and Hashim said once: And Abd al-Rahman bin Awf, and so-and-so, and so-and-so—that the Messenger of Allah (peace and blessings of Allah be upon him) did stone, and we stoned after him. Beware, for there will be after you people who will deny the stoning, and the Dajjal, and the intercession (shafa'ah), and the punishment of the grave, and a people who will emerge from the Fire after they have been charred.