Christ began his address to the bishop with the phrase, “Thus saith the Amen,” which refers to the Old Testament formula, “Thus saith the Lord,” a formula used by the prophets to introduce a message, which would contain, at least, in part, statements from God about his activity in the future.  The Church ends a prayer, creed, or other formal statement, with the term “Amen” to express solemn ratification [so be it] or agreement [it is so].