Catechism of the Catholic Church §1065 — excerpt
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.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.