The saying of the true proverb has happened to them: ‘The dog has returned to its own vomit, and the sow that was bathed to rolling in the mire.’”​—2 Peter 2:20-22.

34, 35. (a) What can we draw from the proverb about the unclean dog and the pig? (b) What should this proverb impress on us?

³⁴ In view of the proverb that Peter quotes, those who take up a life of sin evidently fail to use their opportunities to advance in Christian living. (2 Peter 1:2-11) Some may outwardly abandon bad practices but never come to hate these. They may not really leave behind the “vomit,” the filth, of this world. To them, there still is something attractive about it, and so they can be induced to turn back to it. They may have an inward desire to roll around in the world’s mire of moral degradation. In the case of others, they may fail to increase in appreciation for the value of Christian discipleship, and eventually what the world has to offer takes on greater appeal. How tragic is the fall of those who are thus lured back into the state that had at one time been sickening to them!

³⁵ The inspired proverb stands as a warning lesson to all who claim to be Christian. If we are not cultivating moral and spiritual cleanness in our hearts and lack a real loathing for the filth of this world, we are in grave danger of spiritual ruin. Christians simply cannot afford to let down their guard in resisting the enticements of a corrupt world. We must deaden our wrong desires, not allowing them to gain the mastery over us, nor should we stimulate them by looking with longing to what the world has to offer.​—1 Corinthians 10:12; Colossians 3:5.