The Apostle Paul confessed his sins to the whole world. His letters contain his own summary of his sinful past. Those letters are read and revered by priests and therefore constitute a perpetual communication via the Holy Spirit to them of his confession.
Then if you read Romans 7, a God-breathed part of Holy Scripture, you see Paul's absolution, "Thanks be to God, who delivers me through Jesus Christ our Lord!"
Acts 19 (written by Luke, hence another witness) tells a story which demonstrates that the power of conviction and repentance was present in Paul's ministry:
11 God did extraordinary miracles through Paul, 12 so that even
handkerchiefs and aprons that had touched him were taken to the sick,
and their illnesses were cured and the evil spirits left them.
13 Some Jews who went around driving out evil spirits tried to invoke
the name of the Lord Jesus over those who were demon-possessed. They
would say, “In the name of the Jesus whom Paul preaches, I command you
to come out.” 14 Seven sons of Sceva, a Jewish chief priest, were
doing this. 15 One day the evil spirit answered them, “Jesus I know,
and Paul I know about, but who are you?” 16 Then the man who had the
evil spirit jumped on them and overpowered them all. He gave them such
a beating that they ran out of the house naked and bleeding.
17 When this became known to the Jews and Greeks living in Ephesus,
they were all seized with fear, and the name of the Lord Jesus was
held in high honor. 18 Many of those who believed now came and openly
confessed what they had done. 19 A number who had practiced sorcery
brought their scrolls together and burned them publicly. When they
calculated the value of the scrolls, the total came to fifty thousand
drachmas. 20 In this way the word of the Lord spread widely and grew
Would an unrepentant sinner manifest such a powerful spirit of repentance?