There were people at Rome on Pentecost (
Acts 2:10) who would have heard Peter make the connection in
Acts 2:21 to v38. Even if they didn’t right off the bat, they would have later grew in their understanding (
2 Peter 3:18), as everyone who first becomes a Christian are babes in Christ (
1 Cor. 3:1), and is why we are told to be like newborn babes to desire the pure milk of the word to grow (
1 Peter 2:2), to mature in understanding (
1 Cor. 14:20), that way we can move onto the solid food (
Heb. 5:12-14). They would have matured in understanding and moved onto the meatier things once they were further taught (
Mt. 28:20) or received the letters (Col. 4:16; 1 Thess. 5:27).
Also, they wouldn’t have just started at Romans 10. They would have started at Romans 1, where Paul mentions belief, in Romans 2, where Paul mentions repentance, in Romans 3 and 5, where Paul mentions the blood, as well as grace (also mentioned in Romans 4) in Romans 6, where Paul mentions baptism, in Romans 9, where Paul mentions mercy.
Let us see if they taught the same.
Did Peter mention repentance? Yes (Acts 2 and 3).
Did Paul mention it to the Romans? Yes (Rom. 2).
Did Peter mention baptism? Yes (Acts 2 and 1 Peter 3)
Did Paul mention it to the Romans? Yes (Rom. 6)
Did Peter mention call upon the name of the Lord and connect that with salvation? Yes ( Acts 2)
Did Peter also explain how to do that? Yes (
Acts 2:38)
Did Paul mention call upon the name of the Lord and connect it to salvation? Yes (Rom. 10).
Would Paul’s call upon the name of the Lord (Acts 22:16; cf. Rom. 10:13) be contradictory to what Peter meant on Pentecost (Acts 2)? No (
Gal. 1).
Since both Paul and Peter were inspired by the same Spirit of truth (and since the Spirit cannot lie as He is God and God cannot lie (Titus 1:2), then neither Paul nor Peter would have wrote or taught a contradictory message by the authority of Christ of how to be saved from sin by the precious blood of Jesus, or else both would be accursed, as mentioned above (Gal. 1:6-9).
Is Paul saying to be saved, you must confess Jesus, believe He’s Lord, but calling on the name of the Lord does not also involve having to repent and be baptized for the remission of sins? He wouldn’t be saying it didn’t involve that, because that would be contradicting what the Spirit inspired Peter to say, which would be having the Spirit contradicting Himself. Paul also would not be saying you don’t have to repent and be baptized for the remission of sins in Rom. 10 v9-13, because he himself says Ananias told him to arise, be baptized, and was away thy sins, calling on the name of the Lord (Acts 22:16).
In total: He said to believe (Rom. 1:16), repent (Rom. 2:4), confess (Rom. 10:9-10, and call upon the name of the Lord (v13), which is in perfect and complete harmony with what Peter says calling on the name of the Lord involves. It’s also in complete harmony with Jesus, as Jesus says why call me Lord, Lord, and not do the things which I say (Lk. 6:46). Jesus says to believe (Jn. 3:16), repent (Lk. 10:3), confess (Mt. 10:32-33) and he that believes and is baptized shall be saved (Mk. 16:16). If you want to be saved, you’ll believe and be baptized according to Jesus in Mark 16:16. But believing in Jesus to be saved also involves repenting and confessing He’s Lord. Peter also says believe (Acts 10:43) and to repent and be baptized (Acts 2:38). For what reason are we to believe and to be baptized Peter? For the same reason Jesus inspired him to say by His authority: For the remission of sins.
When you put 10:9-13 together with the whole counsel of God on this subject (Acts 20:27; cf. Ps. 119:160), you don’t get a contradictory message, but a harmonious divine message by two apostles of Christ, who taught the same gospel of salvation, the same doctrine of Christ, and the same way to call upon the name of the Lord to be saved, etc etc.
