There are three perspectives from which to view Christian salvation.
They account for the various theological expressions that were used in the New Testament. Let me explain.
1/ Introduction (Anticipatory)
Introduction of salvation occurs when a Christian leads another person to faith in Christ, as when Paul told the Philippian jailer to believe on Christ for salvation (Acts 16:31). It is also what Peter did on the Day of Pentecost when he preached the resurrected Christ to his fellow Jews to instill faith in Christ for salvation. It would be equivalent to us as Apostolics saying to someone today, “You can be saved if you place your faith/trust in Jesus Christ”. By saying so, we are not leaving off Acts 2:38. We’re leading up to it just as Peter and Paul were.
2/ Revelation (Experiential)
Revelation of salvation occurs when someone tells another person how to be saved, as Peter did on the Day of Pentecost (Acts 2:38) and as Paul did with the Philippian jailer (Acts 16:32-33). It always involves the tenets of salvation. This is why the tenets are so conspicuous in actual instances of salvation (Acts 2:37-39; 8:16-17; 9:17-18; 10:44-48; 19:1-6).
3/ Retrospection (Theological)
Retrospection of salvation occurs when someone looks back on the faith experience of salvation, as if summarizing it. At such a time, he would not regard the tenets of salvation as separate from faith, which they are not. They are actually obeyed due to faith. He would, therefore, view the whole experience of being in Christ as one involving faith because, from beginning to end, everything was done in faith and accomplished by faith— faith which was due to the grace of God. Hence, the many retrospective expressions of Paul regarding salvation in Christ being by faith, such as Ephesians 2:8-9 and Romans 5:1. And, when Paul merely viewed salvation from the standpoint of the grace of God, he styled it simply justification by grace (Romans 3:24; Titus 3:7). None of these retro-looking theological expressions overlook or dismiss the tenets of salvation revealed in Acts 2:38. They encompass them. There is no other salvation in the Christian era (Ephesians 4:5; Galatians 1:8-9; Jude 3).
Conclusion
Faith in Christ is expressed according to the perspective from which salvation is viewed. It is strongly related to tense— future, present, and past. But, at the center, is the all-important plan of salvation, Acts 2:38, which is the actual experience upon which the other two perspectives pivot and to which they refer.