"Keep my decrees and laws, for the person who obeys them will live by them. I am the LORD." (Leviticus 18:5)
Leviticus 18 opens the Holiness Code, the great central section of Leviticus. God commands Israel not to follow the practices of Egypt or Canaan: Keep my decrees and laws, for the person who obeys them will live by them. I am the LORD. St. Paul will quote this verse in Galatians 3 and Romans 10, arguing that the life promised by the law has been fulfilled and surpassed in Christ. The chapter then lists the sexual relations that are forbidden: within close family, with a neighbour's wife, between men, with animals. The prohibitions are not arbitrary; they protect the integrity of family, the dignity of persons, and the distinctiveness of Israel from the surrounding culture.
The Catechism draws from Leviticus 18 the foundational biblical teaching on sexual ethics: sexuality is ordered toward a specific form of covenant love, and acts that violate that order damage both persons and the community. The holiness of the body is not a Platonic disdain for physicality but a celebration of the body as the temple of the Spirit, ordered toward the love that reflects God (CCC 2331). The command is framed by identity: I am the LORD. The ethics flow from the character of the God who commands them.
Brothers and sisters, keep my decrees and you will live by them. The moral law is not a fence that keeps you from living; it is the instruction manual for the life that flourishes. The person who lives within the limits of God's design for sexuality, for family, for the body finds not restriction but the fullness of life that the commandments protect.
Lord God, you are the LORD and your decrees give life to those who keep them. Give us the courage to live by your design for our bodies and our relationships, trusting that your commands lead to fullness of life. Through Christ our Lord. Amen.