Jude warns his readers about false teachers who have infiltrated the church. These teachers twist God's grace to allow sinful behavior and deny Jesus as Lord. Jude cites three examples from the Old Testament of God's judgment against unbelievers: the unfaithful Israelites in the wilderness, fallen angels who abandoned their proper dwelling, and the corrupt cities of Sodom and Gomorrah. Jude urges believers to understand these examples so they can recognize and resist false teachers within the church.