Catechism of the Catholic Church §2670 — excerpt
"No one can say 'Jesus is Lord' except by the Holy Spirit." Every time we begin to pray to Jesus it is the Holy Spirit who draws us on the way of prayer by his prevenient grace.
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.
Also cites: St. Gregory of Nazianzus, Oratio, 31, 28: PG 36, 165