Catechism of the Catholic Church §2135 — excerpt
"You shall worship the Lord your God" (Mt 4:10). Adoring God, praying to him, offering him the worship that belongs to him, fulfilling the promises and vows made to him are acts of the virtue of religion which fall under obedience to the first commandment.
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.