The Holy Spirit is the Third Person of the Trinity (Art. 11, Belgic Confession). He is omnipresent and uncreated, among other divine attributes. He is the sanctifier of God’s people and the sustainer of life. He works with every Christian by leading them to the Word of God and preparing them for Christ. As Calvin states, the Holy Spirit is the bond of our union with Christ by faith (Calvin, Institutes, 3.1).
The Holy Spirit also teaches to the Church to preserve the unity of the Body of Christ. His role is not passive, but active regarding what He does in God’s people. He was sent by Christ Himself in the Pentecost to be a counselor of the Church on earth. When one talks about the Heavenly Father, the Son, and the Holy Spirit, one is referring to the Deity, in contrast, to talk about Jesus, the Incarnated Word. While Christ is the image of the Father, the Spirit reflects the Son. As Basil points out, there is no a subordination of the Spirit to the Father or the Son since there’s an equality between the three Persons.
In Sanctification. Believers are transformed by the Holy Spirit into the image of Christ throughout the Scriptures. That is, the Triune God has revealed Himself to believers by means of the Word in order we can be transformed as Body of Christ. The Holy Spirit acts in Sacraments to impart grace to them. The New Testament registers two Sacraments that Jesus Himself ordained, that is, Water Baptism and the Holy Communion. Since Sacramental acts first teach something about Gods character and His grace and mercy; and secondly, they are a means of grace that God uses to reveal Himself to His people with a defined purpose renewing the Body of Christ, sacraments could be understood as practices established by Christ through Himself or the Church that educate believers into the identity of God in order to strengthen their faith, and where Gods grace is especially present. The sacraments are then a seal of salvation through faith given the Spirit.
In Baptism. In the sacrament of Baptism, God welcomes believers in the church and cleans them from original sin. They are baptized in the Name of the Father, the Son, and the Holy Spirit. This formula emphasizes the Trinity because believers are not baptized by three different gods but by the Triune God. The sacrament itself does not save them, but it is the sign of God’s covenant with His people through Christ. So baptism is based on God’s promise and not on a human decision or profession of faith.
In Communion. In the sacrament of the Lords Supper, God nourishes Christians as members of the Body of Christ. They celebrate Christ’s death and resurrection and his victory on behalf of them on the cross. Thus, the communion is a gift truly given with signs by the Holy Spirit where Christ gives himself and believers respond with a sacrifice of praise. I also believe that although Christ is not present physically, he is present spiritually through the power of the Holy Spirit. This Christ’s presence in the sacrament does not depend on the believer’s faith because the gift is Christ Himself so that he is truly the substance of the Lords Supper.
In Salvation. Since the Holy Spirit also has an active role in the believer’s salvation, it is important to understand that salvation not just an event in the life of believers, but an ongoing process where the Triune God will be working in us. The Apostle Paul explains it to us in the following terms: “For those God foreknew he also predestined to be conformed to the image of his Son, that he might be the firstborn among many brothers and sisters. And those he predestined, he also called; those he called, he also justified; those he justified, he also glorified.” (Rom. 8:29-30, NIV)
One notices here more than an order. We appreciate God’s plan for His children: Predestination-Election, Calling, Justification-Sanctification, and Glorification. As seen, the first step in the process of salvation is election or predestination, where God previously has chosen us before doing anything good or evil. Later, the Spirit, by means of regeneration, imparts God’s life to us. So God regenerates us, he gives us faith, and we are then justified. In the process of salvation, God, through reconciliation, changes our relationship with him. We became children of God when before we were children of wrath (Eph. 2.3). The Holy Spirit then sanctifies us every day for Christ. Finally, the glorification is God’s final work in the process of salvation when he will remove sin from our lives and will welcome into his glory.
In conclusion, the Holy Spirit, besides being our helper, also works in the salvific process as previously stated. The triune God has made Christ known to us, and the Spirit reveals us that Christ is both necessary and sufficient for the salvation of His people. In other words, the Spirit lets us know that Christ is necessary because he is the only door to enter into the kingdom of God, as he claimed: “No one comes to the Father except through me,” (John 14:6, NIV) and also the Spirit reveals us that Christ is sufficient for our salvation. This means that besides God’s grace through Christ, believers do not need more to get saved – works, human agency, etc. Since this knowledge about salvation in Christ alone is explained regarding special revelation in the Scriptures, one should not analyze salvation only in terms of natural revelation or partially in terms of a particular time. The Holy Spirit is who reveals that truth to Christians and who makes them understand what God has revealed in His Word. Then it is the Holy Spirit who brings people to salvation and conviction of their sins and their need of God.