Galatians 1:23
But they had heard only, That he which persecuted us in times past now preacheth the faith which once he destroyed.
Cross-reference
In Acts 9:13, Ananias reports hearing about Saul's harm to saints — the same persecution report that Galatians 1:23 says people heard.
In Acts 9:20, Saul immediately preaches Jesus — this fulfills the report in Galatians 1:23 that the former persecutor now preaches the faith.
In Acts 9:26, the disciples fear Saul because of his past — this explains why they were hearing the report of his conversion.
In 1 Corinthians 15:8-10, Paul himself recounts his persecution and grace — directly parallel to the report in Galatians 1:23 from others.
In 1 Timothy 1:13-14, Paul again describes his former persecution and mercy — echoing the same report of his transformation.
1 Corinthians 15:9 has Paul himself confessing his persecution of the church, directly echoing the same past that Galatians 1:23 summarizes.