Musnad Ahmad 2:221

Yazid narrated to us, Yahya informed us, from Sa'id ibn al-Musayyib, that Umar ibn al-Khattab said: Beware of perishing regarding the verse of stoning, and that a speaker might say: "We do not find two prescribed punishments in the Book of Allah." For I have seen the Messenger of Allah, peace and blessings of Allah be upon him, stone, and we stoned after him.