Jamieson, Fausset and Brown on 2 Peter 2:22

22. But--You need not wonder at the event; for dogs and swine they were before, and dogs and swine they will continue. They "scarcely" (2Pe 2:18) have escaped from their filthy folly, when they again are entangled in it. Then they seduce others who have in like manner "for a little time escaped from them that live in error" (2Pe 2:18). Peter often quoted Proverbs in his First Epistle (1Pe 1:7; 2:17; 4:8, 18); another proof that both Epistles come from the same writer.