Musannaf Ibn Abi Shayba 19:702

Abu Bakr narrated to us, he said: Abu Khalid al-Ahmar narrated to us, from Hajjaj, from Abd al-Malik ibn al-Mughirah al-Ta'ifi, from Ibn Shaddad, from Abu Dharr, who said: We were with the Prophet, may Allah bless him and grant him peace, on a journey, and a man came and confessed that he had committed adultery. The Prophet, may Allah bless him and grant him peace, turned him away three times. When it was the fourth time and [the revelation] descended, the Prophet, may Allah bless him and grant him peace, ordered him, and he was stoned. This weighed heavily upon him [the Prophet], until it was recognized on his face. When the anger had dissipated from him, he said: "O Abu Dharr, your companion has been forgiven." He said: And it used to be said that his repentance is that the prescribed punishment (hadd) be carried out upon him.