Catechism of the Catholic Church §1971 — excerpt
To the Lord's Sermon on the Mount it is fitting to add the moral catechesis of the apostolic teachings, such as Romans 12-15, 1 Corinthians 12-13, Colossians 3-4, Ephesians 4-5, etc.
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.
Whole chapters cited: Romans 14 · 1 Corinthians 5 · 1 Corinthians 6 · 1 Corinthians 7 · 1 Corinthians 8 · 1 Corinthians 9 · 1 Corinthians 10