If you've ever been confused about the Trinity, Fred Sanders just came out with a helpful book called The Deep Things of God: How the Trinity Changes Everything. In chapter 4, "The Shape of the Gospel", Sanders distinguishes the separate but complimentary roles of the Son and the Spirit in salvation:
"We would be in danger of missing the Spirit’s distinctive work by confusing his work with Christ’s," Sanders explains. "The best way to keep them unified is to see their difference."
"A classic way of looking at the two-handedness of God’s work in salvation is the relationship between how the Trinity accomplishes redemption and how the Trinity applies that redemption to us. This idea of redemption accomplished and applied is a handy way of considering salvation in its objective and subjective aspects, even when the two phases of God’s saving work are not correlated with the Son and the Spirit. Redemption would not reach its goal without being applied, but there would be nothing to apply if it were not already accomplished. But recognizing the Son and the Spirit, respectively, as the leading figures in the two phases enriches the idea even more. Christ the Son accomplishes redemption in his own (Spirit-created and Spirit-filled) work. The Holy Spirit applies that finished redemption to us in his own (Son-directed and Son-forming) work. The two works are held together by an inherent unity. The Son and the Spirit are both at work in both phases; nevertheless, the Son takes the lead in accomplishment, and the Spirit takes the lead in application."
Learn more about The Deep Things of God.