Musannaf Ibn Abi Shayba 19:758

Abu Bakr narrated to us, he said: Hafs bin Ghiyath narrated to us, from Hajjaj, from al-Hasan bin Sa'id, from Abdullah bin Shaddad: That a woman was brought to Umar, and she confessed to adultery four times. He said, "If you retract, we will not establish [the punishment] upon you." She said, "Two matters shall not be combined against me: that I commit the indecency and that the prescribed punishment is not established upon me." He said: So he established it upon her.