CATECHISM OF THE CATHOLIC CHURCH
SECOND EDITION

Paragraphs 1062–1066

1062 In Hebrew, amen comes from the same root as the word "believe." This root expresses solidity, trustworthiness, faithfulness. And so we can understand why "Amen" may express both God's faithfulness towards us and our trust in him.
1063 In the book of the prophet Isaiah, we find the expression "God of truth" (literally "God of the Amen"), that is, the God who is faithful to his promises: "He who blesses himself in the land shall bless himself by the God of truth [amen]." Our Lord often used the word "Amen," sometimes repeated, to emphasize the trustworthiness of his teaching, his authority founded on God's truth.
1064 Thus the Creed's final "Amen" repeats and confirms its first words: "I believe." To believe is to say "Amen" to God's words, promises and commandments; to entrust oneself completely to him who is the "Amen" of infinite love and perfect faithfulness. The Christian's everyday life will then be the "Amen" to the "I believe" of our baptismal profession of faith:

May your Creed be for you as a mirror. Look at yourself in it, to see if you believe everything you say you believe. And rejoice in your faith each day.

1065 Jesus Christ himself is the "Amen." He is the definitive "Amen" of the Father's love for us. He takes up and completes our "Amen" to the Father: "For all the promises of God find their Yes in him. That is why we utter the Amen through him, to the glory of God":

Through him, with him, in him,
in the unity of the Holy Spirit,
all glory and honor is yours,
almighty Father,
God, for ever and ever.
AMEN.

1066 In the Symbol of the faith the Church confesses the mystery of the Holy Trinity and of the plan of God's "good pleasure" for all creation: the Father accomplishes the "mystery of his will" by giving his beloved Son and his Holy Spirit for the salvation of the world and for the glory of his name.

Such is the mystery of Christ, revealed and fulfilled in history according to the wisely ordered plan that St. Paul calls the "plan of the mystery" and the patristic tradition will call the "economy of the Word incarnate" or the "economy of salvation."