You cannot substitute an Epistle letter for a command for sinners to obey to obtain remission of their sins...
To sinners....
37 Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do?
38 Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, ...
To saints....
25 Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began,
Paul's gospel is Peter's gospel for there is only one gospel, Ephesians 4:5.
Paul agrees with Peter for they are both guided by the same one Spirit, Ephesians 4:4.
Behold told you to read, Romans 16:24,
-Now to him who is able to establish you according to
my gospel and the preaching of Jesus Christ, according to the revelation of the mystery kept secret since the world began.
Truther, Behold needs to read,
2Thessalonians 1:8 and 2Thessalonians 2:14,
Paul says about his gospel,
-to which he called you by
our gospel, for the obtaining of the glory of our Lord Jesus Christ.
Paul's gospel is Peter's gospel, for there is only one gospel, Ephesians 4:5.
Jesus' gospel must be obeyed, Mark 16:15-16; Acts 2:38,
Paul teaches what will happen if Jesus' gospel is not obeyed,
-2Thessalonians 1:8,
- in flaming fire taking vengeance on those who do not know God and on those who do not
obey the gospel of our Lord Jesus Christ.