Who is Ubaydullah?

Ubaydullah is Ubaydullah ibn Umar ibn Hafs ibn Asim ibn Umar ibn al-Khattab, who died in 147 AH. He narrated from Nafi' and others. There is also Ubaydullah ibn Abdullah ibn Utbah ibn Mas'ud, who died in 98 AH; Al-Bukhari narrated from him on the authority of Ibn Abbas and others. And Ubaydullah ibn Musa ibn Abi al-Mukhtar Badham, Al-Bukhari's shaykh, who died in 213 AH. And Ubaydullah ibn Amr al-Raqqi, who died in 180 AH; Al-Bukhari cited him in ta'liq.