In 2 Peter 2, the apostle Peter deals with the problem of false prophets and teachers in the church. He draws a detailed picture of how these pretend believers operate so true Christians can discern their methods and messages and avoid falling victim to their destructive heresies. Peter emphasizes the severity of the situation: “For it would have been better for them not to have known the way of righteousness, than having known it, to turn from the holy commandment delivered to them. But it has happened to them according to the true proverb: ‘A dog returns to his own vomit’” (2 Peter 2:21–22, NKJV).
These false teachers were acquainted with Jesus Christ’s work in the church enough to understand the basic principles of discipleship, but they had resisted coming to true faith and repentance (2 Peter 2:17–20). Like many religious people, they had intellectual knowledge about Jesus but not heart-level, experiential knowledge that would cause them to fully surrender their lives in obedience to Jesus Christ as Lord and Savior (see Romans 10:1–4). They refused to obey Christ’s command: “If anyone wants to follow after me, let him deny himself, take up his cross daily, and follow me” (Luke 9:23, CSB). Instead, they had gone back to their old sinful ways. To illustrate, Peter cites Proverbs 26:11: “As a dog returns to his own vomit, so a fool repeats his folly” (NKJV).
Peter explains that these false prophets had turned their backs on “the holy commandment delivered to them” (2 Peter 2:21, ESV), which, in New Testament times, was shorthand for the entire message of Scripture. They had rejected the whole truth in God’s Word from Old Testament to New, including the gospel of salvation in Jesus Christ. They had resumed their sin-filled way of life, returning to what was disgusting like a dog revisiting its vomit.
In today’s culture, dogs are beloved pets to most, but they were despised in the ancient world. Dogs roamed in packs, foraged food from rotting flesh and garbage, and were not regarded as pets. In the Old Testament, dogs were considered unclean, revolting, evil-doing scavengers (Exodus 22:31; 1 Kings 14:11; 21:19, 23; Jeremiah 15:3; Psalm 22:16). Jesus used dogs and pigs as metaphors for unholy people who would mock, reject, and blaspheme the gospel when presented to them (Matthew 7:6; 15:26–27). Paul also compared false prophets who had infiltrated the church to dogs, warning Christians to “watch out for those dogs, those evildoers, those mutilators of the flesh” (Philippians 3:2).
Peter seemed certain that any attempt at reforming these false teachers would be a waste of time. He used disturbingly graphic language to portray the absolute depravity of those who reject Jesus Christ and then spend their lives trying to lead the faithful astray. These men were like filthy pigs wallowing in the mud or repulsive dogs eating their own vomit—returning to what is disgusting and vile (2 Peter 2:22). This final comparison is an appropriate elaboration of Peter’s earlier reference to false teachers as “brute beasts made to be caught and destroyed” who “speak evil of the things they do not understand” (2 Peter 2:12, NKJV). The apostle’s final verdict was that they would “utterly perish in their own corruption” (2 Peter 2:12, NKJV). These heretics were doomed for destruction.
In 2 Peter 1:5–11, the apostle teaches that perseverance is essential to the Christian life and a mark of genuine faith. There will always be false prophets and false teachers infiltrating Christ’s true body, attempting to trip up and deceive as many as possible (Matthew 24:11, 24; Acts 20:29– 30; Galatians 1:6– 9; 1 Timothy 1:3–7; 1 John 2:18–19). There will be individuals who appear to be true believers but are not (Matthew 7:21–23; Jude 1:3–4). As a dog returns to his own vomit, there will be people in the church who “get tangled up and enslaved by sin again” (2 Peter 2:22, NLT). But born-again believers will not return to the vomit of the past. They will, by the grace of God and the power of the Holy Spirit, pursue a life of godliness and are guaranteed the reward of eternal life (Matthew 10:22; 24:12–13; John 15:4–10; Hebrews 3:14; 10:36–38; 2 Peter 3:11–18; 2 Timothy 4:7–8; James 1:12).