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23 But [de] they had [en] heard [akouo] only, [monon] That [hoti] he which
persecuted [dioko] us [hemas] in times past [pote] now [nun] preacheth [euaggelizo] the
faith [pistis] which [hos] once [pote] he destroyed. [portheo]KJV-Interlinear
23 but
only, they kept hearing, "He who once persecuted us is now preaching the
faith which he once tried to destroy." NASB
In Acts 26:26, it is made clear that Pauls conversion to Christianity was not done in secret, but was pubic and widely known.
And even in this early time, just after his faith in Christ, his history and reputation had preceded him both in the good and in the bad. And especially the change from bad to good, was well known.
Had heard, 'en akouo,' means to keep on hearing, as in hearing some news over and over, again and again. The gossip as it were, or news regarding Paul and the things that affected the new Christian church, were consistent and repeated with regard to Paul, his early attempts to destroy the church, and his subsequent conversion.
The story of Paul, or Saul, and his trip on the Damascus road and encounter with Jesus, were well known. Like wild fire, this news traveled fast.
And this also tells us that the news of Jesus, the Cross, and the many other things related to those early Christian years, traveled fast and spread fast, and not only locally in Jerusalem and Judea but throughout the surrounding region.
By the time Paul entered some new geographical area, the people there already knew of him.
In his earlier years, Paul was not well known, if at all. These folks did not know Paul by his face, but only by his reputation as a persecutor of Christians.
And remember that the persecutions of the Christians did not really get started until after the Cross.
The cross occurred approximately between 30 and 33 A.D. Most historians put it at 32 A.D. Pauls conversion did not occur until about 34-35 A.D., which is only a couple of years following the Cross.
So his persecutions and reputation occurred rapidly after the Cross, and just as rapidly, they changed after his conversion. News had already spread throughout the region.
Pauls missionary journeys began in the mid 40's A.D. and his writings began in the late 40's A.D. and continued until just before his death in the late 60's A.D. He died in 68 A.D.
The faith described here, is not only the means of salvation by faith, but includes his teaching of the entire realm of doctrine, of which he wrote in his many writings, and of which we have in the New Testament today.
So, in those early years following his conversion, though most of that time is not documented, Paul taught scripture and the many new principles of doctrine which are applicable to the New Testament scriptures, and the fulfillment of the Old Testament scriptures.
And, he was known far and wide, for his involvement in Christianity, even in those early years.