Catechism of the Catholic Church §741 — excerpt
"The Spirit helps us in our weakness; for we do not know how to pray as we ought, but the Spirit himself intercedes with sighs too deep for words."
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.