Musannaf Ibn Abi Shayba 18:43

Abu Bakr narrated to us, he said: Abu Mu'awiyah narrated to us, from Hajjaj, from Qatadah, from al-Hasan, he said: The Messenger of Allah (may Allah bless him and grant him peace) said: "The one killed by a whip or a stick is [a case of] quasi-intentional [homicide]."