The cross was a Roman instrument of execution — deliberately brutal, shameful, and public, reserved for slaves and rebels. To die on a cross was to die accursed. That the central symbol of Christianity should be a cross is a scandal the New Testament never hides: the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.
By dying on the cross, Jesus turned the emblem of shame into the sign of salvation. Paul refused to boast in anything else: God forbid that I should glory, save in the cross of our Lord Jesus Christ. To take up one's cross is to follow Jesus in self-denial and surrender. The worst thing humans ever made became, in God's hands, the best thing that ever happened to the world.
The Cross in Scripture
For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.