علي بن موسى الرضا
His father bestowed upon him the surname "Abul-Hasan", after the surnames given to his grandfather Ali al-Ridha and his great grandfather Musa al-Kadhim. To differentiate between these three Abul Hasan, narrators usually call Musa al-Kadhim, abul Hasan the first, call Ali al-Ridha, Abul Hasan the second and call al-Hadi Abul Hasan the third.