When we believe in Christ, Paul said in verse 17 of our Bible reading, if anyone is in Christ, he is a new creation. The old has passed away; behold, the new has come. All this is from God, who through Christ reconciled us to Himself and gave us the ministry of reconciliation.

Jesus died for us; and our old unbelieving, rebellious self-died in Him. And now our new believing-selves live. God does this through His Spirit. He penetrates into the inmost being of man, open the closed heart, softens the hard heart, and circumcises the heart that is uncircumcised.

(Canons of Dort, Chapter 3)