Catechism of the Catholic Church §447 — excerpt
Jesus ascribes this title to himself in a veiled way when he disputes with the Pharisees about the meaning of Psalm 110, but also in an explicit way when he addresses his apostles.
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.