But God forbid that I should boast except in the cross of our Lord Jesus Christ

Galatians 6:14
But God forbid that I should boast except in the cross of our Lord Jesus Christ, by whom[a] the world has been crucified to me, and I to the world.

Paul has a deep understanding of Scriptures before he came to know Christ. When he encountered the Lord, all his doctrines made complete sense especially the work of our Lord on the Cross. This sacrificial work is a stumbling block to some and foolishness to others. Yet, when we go out and preach the gospel, the preaching of the work of the Cross must not be diminished in any way. To ignore what was accomplished at the Cross is to rob the Salvation message of its power and the whole reason that our Lord came to die for our sins.