Zac Poonen discusses the transformation from the old man to the new man in Christ, emphasizing that while the old man, representing our sinful nature, has been crucified, the new man desires to do God's will. He illustrates the difference between a disciple who may fall into sin and an unbeliever who willingly chooses it, comparing it to a cat and a pig in dirty water. Poonen stresses the importance of nurturing the new nature through the Word of God and prayer to resist sinful desires. He clarifies that falling into sin is different from practicing sin, providing comfort that believers have an Advocate in Jesus when they stumble.

We have already seen how the old man was like an unfaithful servant who allowed the thieves to enter the home. That old man however has been crucified, put off and buried. There is a new man now within us, who says, "Behold I have come to do Thy will, O God" (Heb. 10:7). Yet we know that it's possible for a disciple of Jesus to sin. But there is a difference between a disciple sinning and an unbeliever sinning, just as there is a difference between a cat falling into dirty water and a pig choosing to jump into the dirty water! The cat hates the dirty water, but may fall into it accidentally. The pig, however, loves it. It's all a question of nature. The disciple of Jesus has a new nature that loves purity and hates sin. The old man wants to sin. The new man never wants to sin. But if the new man is not strong enough, he may not be able to keep the door of his heart shut against the desires of the flesh. That's not because he wants those desires. No. But because he is not strong enough to resist them. This may be, because he has not fed himself sufficiently on the Word of God, or because he has not strengthened himself through prayer. So, there's a difference between committing sin and falling into sin. It's important to know this difference; for we can then avoid a lot of unnecessary feelings of condemnation in our heart. The Bible says that "the one who practises sin (that is, one who keeps on committing sin deliberately) is of the devil" (1 Jn. 3:8). On the other hand, he writes to believers saying, "If anyone sins (that is, if one falls into sin accidentally), we have an Advocate with the Father, Jesus Christ the righteous; and He is the propitiation for our sins" (1 Jn. 2:1,2).