Musnad Ahmad 1017:15

Abu Nu'aym narrated to us, Bashir narrated to us, 'Abdullah ibn Buraydah narrated to me, from his father, who said: I was sitting with the Prophet, peace and blessings of Allah be upon him, when a woman from Ghamid came to him and said: "O Prophet of Allah, I have committed adultery, and I want you to purify me." The Prophet, peace and blessings of Allah be upon him, said to her: "Go back." When the next day came, she came to him again and confessed to him about the adultery, saying: "O Messenger of Allah, I have committed adultery, and I want you to purify me." The Prophet, peace and blessings of Allah be upon him, said to her: "Go back." When the next day came, she came to him again and confessed to him about the adultery, saying: "O Prophet of Allah, purify me, for perhaps you will turn me away as you turned away Ma'iz ibn Malik. By Allah, I am pregnant." The Prophet, peace and blessings of Allah be upon him, said to her: "Go back until you give birth." When she gave birth, she came with the child, carrying him, and said: "O Prophet of Allah, this is he whom I have given birth to." He said: "Go and breastfeed him until you wean him." When she weaned him, she came with the child, in whose hand was a piece of bread. She said: "O Prophet of Allah, I have weaned him." The Prophet, peace and blessings of Allah be upon him, ordered that the child be taken and handed him over to a man among the Muslims. He then ordered that a pit be dug for her, and she was placed in it up to her chest. Then he ordered the people to stone her. Khalid ibn al-Walid came forward with a stone and threw it at her head, and blood splattered onto Khalid's cheek, so he cursed her. The Prophet, peace and blessings of Allah be upon him, heard his cursing of her and said: "Gently, O Khalid ibn al-Walid. Do not curse her, for by the One in Whose hand is my soul, she has repented with a repentance such that if the collector of illegal taxes had repented it, he would have been forgiven." Then he ordered that she be prayed over, and she was buried.