The Leather Saint(1956)

Episcopalian minister Gil Allen keeps up his college days interest in boxing by working out at a gym run by his friend, Tom Kelley but declines offers to fight in an actual staged bout, until he realizes he could use the prize money to purchase equipment for local polio victims. Keeping his real identity secret and hoping to step away after one big payday, Gil signs a contract to fight for greedy promoter Gus MacAuliffe.