Musannaf Ibn Abi Shayba 18:591

Abu Bakr narrated to us, he said: Yahya ibn Adam narrated to us, from Zuhayr, from al-Hasan ibn 'Umarah, from al-Hakam, who said: The driver, the one intending a destination, and the rider are liable for what their mount inflicts with its hand or foot, or if it kicks or strikes.