1 Timothy 1:12
And I thank Christ Jesus our Lord, who hath enabled me, for that he counted me faithful, putting me into the ministry; And I thank Christ Jesus our Lord, who hath enabled me, for that he counted me faithful, putting me into the ministry;
The verse is Paul's thanksgiving to Christ Jesus our Lord for enabling him with strength for service and for counting him faithful by putting him into the ministry. The enabling is Christ giving strength to carry out the work entrusted, and the counting faithful is Christ appointing to ministry those he counts faithful to serve. This is how Christ still appoints to service those he counts faithful.
Christ gave Paul this enabling and appointment despite his former life as a blasphemer, persecutor, and violent man who violently opposed believers. Paul received mercy because he did what he did in ignorance and unbelief, acting ignorantly in unbelief. Christ's abundant grace brought Paul faith and love, and his change shows that Christ's grace and faith can transform even so great a sinner.
Paul was made an example to others who would afterward believe. His example shows that people living in error may still be serving God conscientiously. Such ones can be changed by Christ's revelation and grace.