interjection 1.it is so; so be it (used after a prayer, creed, or other formal statement to express solemn ratification or agreement). adverb 2.verily; truly. noun 3.an utterance of the interjection amen. 4.a musical setting for such an utterance. 5.an expression of concurrence or assent: The committee gave its amen to the proposal.
/\ dictionary.com.
Whether Christ actually said it or not, I don't know, but I would say look into one's Bible.