The Quinisext Council (Trullo, 692)

Called Penthekte, the fifth-and-sixth, because it supplied the canons that the Fifth and Sixth Ecumenical Councils had not issued, both having ruled on doctrine alone. Its 102 canons are the backbone of Orthodox canon law: they settle the scriptural canon by receiving the earlier lists, regulate the clergy, forbid depicting Christ as a lamb in place of His human form, and legislate on fasting and marriage. The Orthodox Church receives them as having the authority of the Sixth Council; Rome never accepted them in full, which is itself one of the older fault lines between East and West.