Acts 2:21 And it shall come to pass, that whosoever shall call on the name of the Lord shall be saved.
This conditional promise of Salvation comes to us from Peter’s sermon on the Day of Pentecost: if you call, then you will be saved. But it is not the ”calling” that is the cause of your salvation, for it is actually the now poured-out Holy Spirit who is calling us by the Gospel. The Spirit creates the faith that calls out and receives the gift of the Spirit and the gift of Salvation.
It has been described as looking sort of like this: the Holy Spirit hovers over the person and convicts him through the preached and heard Gospel, and then He drops into the heart when the convinced sinner opens the heart. This ”conversion process” happens at baptism, or whenever the sinner comes to faith.
The promise is twofold: the first is the indwelling Spirit coming to live in our spirit; the second is that we shall be saved. We are saved from Sin: all sins are forgiven and we receive the righteousness of God through faith. We are saved from Death: we are given eternal life now and that life continues through and beyond physical death. We are saved from the power of the Devil: although he lies and claims to have power over us he does not. We are saved for good works that we shall walk in them: the indwelling Spirit is sanctifying us to slowly mold us into becoming the holy, righteous people we have been already declared to be. We trust His promise that we are becoming more Christlike, shaped into the image of God. This promise is a result of being saved and of the indwelling Spirit.