Emperor Theodosius II commissions in 429 a compilation of all imperial constitutions since Constantine I, completed February 15, 438: 16 books, over 2,500 constitutions (311-437), promulgated in both halves of the empire January 1, 439. Per historian John F. Matthews, it is the first official public compilation of Roman law since the Twelve Tables. Book XVI is the most complete source on Christian religious legislation of the late Empire.