The final member of the Godhead and often missing in most theological discussions (except for sanctification) is the Holy Spirit. Sanctification has been historically is the one area where the Holy Spirit is given room to be discussed. So much of what is said may not be new, but it should still be encouraging.
The Holy Spirit Secures Us
First It is the Holy Spirit who seals the saints as God’s own until the final days. The Holy Spirit is at work in every believer’s life guaranteeing their salvation and continual sanctification. Ephesians 1:12–14 is key to understanding this role of the Spirit: “And you also were included in Christ when you heard the message of truth, the gospel of your salvation. When you believed, you were marked in him with a seal, the promised Holy Spirit, who is a deposit guaranteeing our inheritance until the redemption of those who are God’s possession—to the praise of his glory.” Paul reinforces the fact that it is the Spirit that will protect and secure all believers throughout their lives. Dietrich Bonheoffer did extensive work drawing out the work of the Spirit as the “sealer” of faith. He focuses first on the fact that this seal is proof of the salvation believers have received in Christ, and explains three distinct ways this sealing maintains a Christian’s faith. First, It will keep them separated from the world, Second, it will maintain their walk in a way worthy of their calling, and finally it will secure their faith in the life of Christ himself.
Holy Spirit Grows Us
Besides the sealing work of the Spirit in sanctification, The Holy Spirit also serves as the direct agent bringing about holiness in the lives of the saints. He gives man the ability to pursue holiness along with the desire to run hard after Him. Kenneth Boa points out that the role of the Holy Spirit is “bearing witness to Jesus Christ, applying Christ’s redemptive work in human hearts, and working personally and progressively to form Christ likeness in the lives of believers.” . It is left to the Spirit to complete the work orchestrated by the Father and begun by the Son. Scriptural evidence for this role of the Spirit can be seen in 1 Corinthians 6:11: “And that is what some of you were. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.” This passage clearly articulate that the Spirit is the one at work in active sanctification,
He Convicts Us
The working of the Holy Spirit in the lives of believers takes many different forms to produce holy lives in believers before the throne. The Holy Spirit’s work in sanctifying believers also takes on the role of convicting believers of their sins. John 16:8–11 reveals that “when he comes, he will prove the world to be in the wrong about sin and righteousness and judgment: about sin, because people do not believe in me; about righteousness, because I am going to the Father, where you can see me no longer; and about judgment, because the prince of this world now stands condemned.” The role of convicting believers of their sins, either active or passive, is an important one. Here the Spirit is able to correct actions before they become habits that are destructive to a believer’s life. Believers, however, do have the ability to ignore this call of the Spirit. Ephesians warns believers not to quench the Spirit. Here it is important to see that sin does cause the Spirit to be grieved and believers should not shrug it off. To grieve the Spirit is a serious offense taken seriously.
He Teaches Us
Here it is seen that “Jesus promised his disciples that the Spirit of truth would ‘guide you into all truth’ and ‘disclose to you what is to come’ (John 16:13). The divine anointing teaches us (1 John 2:27), and the Spirit glorifies the Son making Jesus’ words Known to us (John 16:14).” The Spirit is working in the hearts of believers to teach them the truth of the Lord, and is connected with his role as convicting believers of their sin. The illumination of the scriptures themselves reflects this truth. As a believers read scripture it is the Spirit that illuminates the truth of who God is and how man is to respond to him and his calling on their lives.
He is the Active Agent of Prayer
The final role of the Spirit is the role of prayer. Romans 8 26-27 focuses on the Spirit’s involvement in the prayer life of believers. “In the same way, the Spirit helps us in our weakness. We do not know what we ought to pray for, but the Spirit himself intercedes for us through wordless groans. And he who searches our hearts knows the mind of the Spirit, because the Spirit intercedes for God’s people in accordance with the will of God.” Paul teaches that the Spirit is active in bringing the needs of believers to the throne of the Father.
The Holy Spirit plays an important role as the active agent in the lives of believers that brings about a holy life before God. He serves as the one who teaches believers the meaning of righteousness convicting them when they go astray. In teaching and convicting He grows them to a deeper understanding of the truth. All of these are connected directly to His work of sealing believers to the Day of Judgment. In the end, all three members have a specific function in bringing about holiness in the lives of believers.
 Dietrich Bonheoffer. The Cost of Discipleship (New York, Touchstone, 1959), 278
 Ibid. 279
 Kenneth Boa, Conformed to His Image: Biblical and Practical Approaches to Spiritual Formation (Grand Rapids, Zondervan 2001), 292.
 Mark Boda, A Severe Mercy: Sin and Its Remedy in the Old Testament (Winona Lake, Eisenbrauns, 2009), 293
 Millard Erickson, Christian Theology 2nd Edition (Grand Rapids, Baker Books, 1998), 874.
[6 Boda, 293
 Erickson, 875
 Boa, 294