Musnad Ahmad 790:139

'Affan narrated to us, Aban—meaning al-'Attar—narrated to us, Yahya ibn Abi Kathir narrated to us, from Abu Qilabah, from Abu al-Muhallab, from 'Imran ibn Husayn, that a woman from Juhaynah came to the Prophet of Allah, may Allah bless him and grant him peace, and said to him: "I have committed a transgression that warrants a prescribed punishment (hadd), so execute it upon me," and she was pregnant. He ordered that she be treated well until she gave birth. When she gave birth, she was brought to the Messenger of Allah, may Allah bless him and grant him peace. He ordered that her clothes be fastened upon her, then he had her stoned, and then he prayed over her. 'Umar said: "O Prophet of Allah, do you pray over her when she has committed adultery?" He said: "She has repented with a repentance that, if it were divided among seventy of the people of Medina, it would suffice them. And have you found anything better than that she gave her soul for the sake of Allah?"