What does it mean to say that for Paul justification by faith was a weapon with which to contend?

EPISODE #193: Ted asks about what Paul meant when he spoke about justification by faith, reading a quote from author F.F. Bruce. Rod talks about how we see in the writings of Paul that Jesus’ words divide, Jesus’ connection to the Old Testament, what was expected of the Messiah when He arrived, and the contrast between Who Jesus is and His claims and actions versus all the other religions of the world.