The heart is were the Human Spirit resides.
That Happens instantly, when we FIRST GENUINELY BELIEVE, which is SALVATION. Reference John 3:6.
John 3:6 (NIV)
6 Flesh gives birth to flesh, but the Spirit gives birth to spirit.
Sanctification is disciplining to body to work out what is already in the HEART. In other words:
Ephesians 5:1-2 (HCSB)
1 Therefore, be imitators of God, as dearly loved children.
2 And walk in love, as the Messiah also loved us and gave Himself for us, a sacrificial and fragrant offering to God.
Colossians 2:6 (NKJV)
6 As you have therefore received Christ Jesus the Lord, so walk in Him,
1 Thessalonians 4:1 (HCSB)
1 Finally then, brothers, we ask and encourage you in the Lord Jesus, that as you have received from us how you must walk and please God—as you are doing—do so even more.
1 John 1:7 (HCSB)
7 But if we walk in the light as He Himself is in the light, we have fellowship with one another, and the blood of Jesus His Son cleanses us from all sin.
1 John 2:6 (HCSB)
6 The one who says he remains in Him should walk just as He walked.
Sanctification is OUR WALK, and it will take a LIFE TIME TO LEARN TO BE LIKE HIM.