… you have put off the old self …. and have put on the new self, which is being renewed in knowledge after the image of its creator. (Colossians 3:9-10)
Here ‘new’ is neos—young, vigorous. Ephesians 4:22-24 repeats the contrast but uses kainos—fresh, newly made—to stress quality. Jesus unites the words in His parable: turbulent neos wine must be poured into kainos (supple) wineskins (Matthew 9:17) lest both be ruined. Regeneration is likewise a once-for-all exchange: the lifeless old man is stripped away and the newly created kainos man donned. Yet the neos life inside keeps surging, demanding ongoing renewal in the spirit of your mind. This lifelong process flows from “learning Christ”—not classroom theory but living union with Him. As a hedge drops dead leaves when new sap rises, the believer sheds the past while Christ’s righteous, holy character grows visibly, proving that truth is in Jesus (Ephesians 4:21).