Expiation for Unfulfilled Oaths

Bukhari :: Book 8 :: Volume 79 :: Hadith 703

Narrated Al-Ju'aid bin Abdur-Rahman:

As-Sa'ib bin Yazid said, "The Sa' at the time of the Prophet was equal to one Mudd plus one-third of a Mudd of your time, and then it was increased in the time of Caliph 'Umar bin 'Abdul Aziz."