What are willies marks of sins

Willie wakes up on Saturday morning with a pain in his stomach. He has wet himself during the night. Tom finds Willie under the bed and helps clean him off. Willie apologizes. Even though it is very hot out, Willie insists on wearing socks so that others can’t see his “marks of sin.” Willie feels ashamed as Tom cleans his mattress outside, believing that everyone will see it and think he is wicked.