Roman Catechism 42.19

Chapter 42 — Part IV: Prayer — Amen

Section 19. Other Explanations Of The Word "Amen" — By many, the word amen is differently interpreted. The Septuagint interprets it, So be it; others translate it, Verily: Aquila renders it, Faithfully. Which of these versions we adopt, is a matter of little importance, provided we understand the word to have the sense already mentioned, namely, that when the priest (pronounces Amen), it signifies the concession of what hag been prayed for. This interpretation is supported by St- Paul in his Epistle to the Corinthians, where he says: All the promises of God are in him, "it is"; therefore also by him, amen to God, unto our glory.