What cancels the work of the cross?
Any human work added to salvation—such as circumcision, church membership, or baptism—cancels the work of the cross. Depending on something you can do in the flesh to fulfill salvation nullifies what Christ accomplished, for His finished work on the cross is complete and sufficient.
Les explains that if a person is doing something to fulfill salvation—or to put the frosting on the cake—they are lost, because Christ can profit them nothing. The only way anyone enters God's heaven is because of what Christ profits us on our behalf. Les warns people not to depend on something they can do. In this case it was circumcision, but it can be anything: church membership, baptism, or anything done in the flesh. When you do it as part of salvation, you cancel the work of the cross. Always remember that when Christ said, "It's finished," He meant what He said; everything we need was accomplished on that cross.