Matthew 5 opens the Sermon on the Mount (Matthew 5–7). Luke 6 gives a shorter version on a level place (6:17), right after Jesus prays all night and chooses the Twelve (6:12–16). The sermon starts with the Beatitudes (Matthew 5:3–12), which Luke pairs with four matching woes (Luke 6:20–26). Then come salt and light (Matthew 5:13–16) and six contrasts that begin “Ye have heard that it was said… But I say unto you” (5:21–47): anger, lust, divorce, oaths, retaliation and enemies. Each one takes an old command about actions and aims it at the heart. The chapter ends with “Be ye therefore perfect” (5:48).
A few study helps your youth will love. The Joseph Smith Translation and 3 Nephi 12:22 both leave out “without a cause” in Matthew 5:22 (see the footnote), so the Savior’s standard on anger is higher than it first looks. Matthew 5:23–24 (be reconciled before you bring your gift to the altar) speaks directly to priests who bless the sacrament. The Book of Mormon version of the sermon adds important words: “blessed are the poor in spirit who come unto me” (3 Nephi 12:3), and after His Resurrection the Savior says “perfect even as I, or your Father” (3 Nephi 12:48). The footnote on Matthew 5:48 explains that the Greek word means complete, finished, fully developed.
For 16- to 18-year-olds, this chapter lands right on top of perfectionism: college applications, scholarships, mission standards, sports and a phone full of other people’s highlight reels. Jesus’s Beatitudes flip the world’s idea of “blessed,” and Luke’s last woe (“when all men shall speak well of you,” 6:26) stings in a world of likes and follower counts. Jeffrey R. Holland’s October 2017 talk “Be Ye Therefore Perfect—Eventually” says that teenagers and missionaries often tell him they are not good enough, and teaches that perfection is a gift received through Christ over time (see Moroni 10:32). Share it with confidence.
Handle Matthew 5:27–28 gently and simply. The Savior teaches that purity begins in our thoughts; For the Strength of Youth: A Guide for Making Choices (“Your Body Is Sacred”) is a great companion. Don’t single anyone out, keep the emphasis on hope and repentance, and if a youth comes to you privately, listen warmly and point them to their parents and bishop. Shame is never the Savior’s tool.