The Catechism in Questions & Answers

332. What is the significance of the Fifth Commandment in the New Testament?

Jesus did not confine the observance of this commandment to its literal fulfilment. The important thing for Him was the individual’s inner attitude. It was for this reason that He said: “You have heard that it was said to those of old, ‘You shall not murder, and whoever murders will be in danger of the judgement.’ But I say to you that whoever is angry with his brother without a cause shall be in danger of the judgement’” (Matthew 5: 21-22). In 1 John 3: 15 the Apostle supplements this as follows: “Whoever hates his brother is a murderer.”