Musannaf Ibn Abi Shayba 19:335

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Ibn Abi ‘Arubah, from ‘Abdullah al-Danaj, from Husayn Abu Sasan, that the people of Kufa rode to ‘Uthman and informed him of what had happened regarding the affair of al-Walid ibn ‘Uqbah concerning the drinking of wine. So ‘Ali was spoken to regarding that, and ‘Uthman said: "Take your cousin and carry out the prescribed punishment (hadd) upon him." He (‘Ali) said: "Stand up, O Hasan, and flog him." He (Hasan) said: "What do you have to do with this? Let someone else do this." He (‘Ali) said: "Rather, you have become weak, feeble, and incapable. Stand up, O ‘Abdullah ibn Ja‘far." So he began to flog him, and ‘Ali counted until he reached forty. He then said: "Stop, and hold back." He (then said): "The Messenger of Allah (ﷺ) flogged forty, and Abu Bakr flogged forty, and ‘Umar completed it to eighty, and all of it is Sunnah."