Baptism is a symbol of the end of the old you and the beginning of the new you. It’s an outward showing of an inward doing, because regeneration takes place when we believe in Jesus.
The Bible tells us, Therefore we were buried with Him through baptism into death, that just as Christ was raised from the dead by the glory of the Father, even so we also should walk in newness of life (Romans 6:4 )
By the way, there is God’s part and our part. God sanctifies us. The apostle Paul wrote to the Thessalonian church, “May the God of peace Himself sanctify you completely; and may your whole spirit, soul, and body be preserved blameless at the coming of our Lord Jesus Christ (1 Thessalonians 5:23 )
But then we need to cooperate with God. Paul wrote to the believers in Philippi, Work out your own salvation with fear and trembling; for it is God who works in you both to will and to do for His good pleasure (Philippians 2:12–1)
Notice that Paul didn’t say, Work for your salvation. That’s impossible, because salvation is a gift of God. Rather, live it out. Experience it. Our salvation should affect us in our day-to-day choices.
Salvation is coming to Christ; sanctification is growing in Christ. Salvation happens in a moment, bringing a sinner from spiritual death to life; sanctification is an ongoing process.
Salvation is being forgiven of the past; sanctification is breaking free from the power of sin. This is something God does in our lives, and it never stops until we get to Heaven.