Believers are saved through the gospel of Christ. It comes with much assurance. The Spirit of grace enables us to believe in Christ. When the gospel comes in the power of the Holy Spirit, we have much assurance. Only the Holy Spirit can give the believer this assurance. For our gospel did not come to you in word only, but also in power, and in the Holy Spirit and in much assurance (1 Thessalonians 1:5).
Believing the gospel of Christ is our salvation (1 Corinthians 15:1-4). Never does God believe for us. However, God enables you to truly repent and believe in Christ. The grace of God enables us to repent and believe on the Lord Jesus Christ. After you repent and believe the gospel, you can testify how God brought you to that point. It is the power of God unto salvation to all who believe (Romans 1:16).
The Holy Spirit convinces believers of the gospel with much assurance. Without the Spirit of grace convincing you, there is no desire to be saved. The Holy Spirit convicts of unbelief and convinces us to turn to God by faith in the Lord Jesus Christ (John 16:8-11). That's the Holy Spirit working in believers through the gospel.
The Holy Spirit enables us to repent and believe on the Lord Jesus Christ (Acts 17:30; 16:30-31). Our inability to do so is overcome only by looking to the Lord Jesus Christ (Hebrews 12:2). What God commands, God provides through the Holy Spirit. He who commands repentance, grants us repentance (2 Timothy 2:25). He who commands faith in Christ, gives us faith by the word of God (Romans 10:17).
