Catechism of the Catholic Church §2049 — excerpt
The Magisterium of the Pastors of the Church in moral matters is ordinarily exercised in catechesis and preaching, on the basis of the Decalogue which states the principles of moral life valid for every man.
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.