20 But you, dear friends, build yourselves up in your most holy faith and pray in the Holy Spirit. 21 Keep yourselves in God’s love as you wait for the mercy of our Lord Jesus Christ to bring you to eternal life. 22 Be merciful to those who doubt; 23 snatch others from the fire and save them; to others show mercy, mixed with fear—hating even the clothing stained by corrupted flesh.
Fellowship with the family of God is necessary for our safety and maturity.
Jude (most commentators think that this is Jesus' half-brother) is warning his readers that there are false teachers among them and they must be on their guard against their teaching. These people will be punished for their false teaching just as history has shown that God punishes those who are wicked and sinful. But the family of God must protect each other. We must build each other up, praying for one another and keeping each other safe. Show mercy and grace to those who are struggling in the faith. Confront them regarding their sins being careful to separate the sin from the sinner. In other words loving the person and hating the sin.
Let us not neglect doing life together as the family of God, giving family members access to the struggles of our lives so that they can confront, encourage and walk alongside us in this journey of faith. Be a part of a GROW group. Be involved in a ministry group. These things provide the fellowship and interaction we need to help us stay faithful.