How should we interpret Our Lord’s words in the Sermon on the Mount, “So be perfect, just as your heavenly Father is perfect” (Mt 5:48)?

Taken literally, these words do seem to command the impossible. Try to become perfect and you will quickly see you cannot do it. The more you try, the more you turn inward, focusing on your every act, thought, word. Your effort only makes you more and more self-centered and miserable, and less and less “perfect.”

The Greek word translated as “perfect” is teleios (teleioi in the plural). It means, “brought to completion; fully accomplished, fully developed; fully realized.” The word “therefore” in Matthew 5:48 is significant. It marks that verse as a summary of that chapter and, indeed, as a summary of the entire sermon.

The Second Vatican Council summed up Jesus’ command in these words: “The followers of Christ . . . [have] become sons of God and sharers in the divine nature. In this way they are really made holy. Then, too, by God’s gift, they must hold on to and complete in their lives this holiness they have received” (Lumen Gentium, No. 40).