Musannaf Ibn Abi Shayba 19:532

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Sufyan, from ‘Amr ibn Abi Sufyan, that a thief was brought to Ibn al-Zubayr, so he cut him. Aban ibn ‘Uthman said to him, "Cauterize him." He said to him, "You are indeed merciful toward him." He said, "No, but it is from the Sunnah."