How does the Spirit apply to us the redemption purchased by Christ?

The Spirit applies to us the redemption purchased by Christ, by working faith in us, and thereby uniting us to Christ in our effectual calling.

“For by grace you have been saved through faith; and that not of yourselves, it is the gift of God.” ~ Ephesians 2:8 (NASB)

Salvation is the gift of God, every part of it, for we are not saved because we believe in Christ, we believe in Christ because we are saved by grace through faith; faith is, therefore, the vehicle through which we are brought to Christ.

“So that Christ may dwell in your hearts through faith...God is faithful, through whom you were called into fellowship with His Son, Jesus Christ our Lord.” ~ Ephesians 3:17 & 1 Corinthians 1:9 (NASB)

Fellowship with the Son is an effectual calling. Jesus said, “All that the Father gives Me will come to Me, and the one who comes to Me I will certainly not cast out.” ~ John 6:37 (NASB)