But you, beloved, by building yourselves up in your most holy faith and praying in the Holy Spirit,
Believers must build themselves up in faith and pray in the Holy Spirit.
This verse begins Jude's positive summons to persevering life.
17But you, beloved, remember what was foretold by the apostles of our Lord Jesus Christ 18when they said to you, “In the last times there will be scoffers who will follow after their own ungodly desires.” 19These are the ones who cause divisions, who are worldly and devoid of the Spirit. 20But you, beloved, by building yourselves up in your most holy faith and praying in the Holy Spirit, 21keep yourselves in the love of God as you await the mercy of our Lord Jesus Christ to bring you eternal life. 22And indeed, have mercy on those who doubt; 23save others by snatching them from the fire; and to still others show mercy tempered with fear, hating even the clothing stained by the flesh.