1 Corinthians 1:18 For the preaching of the cross is to them that perish foolishness; but unto us which are saved it is the power of God.
This verse tells us that there is an unbelieving world out there that believes the preaching of the gospel is foolish. Everyone is in the process of either coming to the a life of salvation or going in the other direction to a life of destruction. It is hard for the unbeliever to accept what Christ did on the cross for us in shedding His blood for the forgiveness of sin. They actually believe this to be nonsense. For us that are believers we understand the power of the cross and just what it took for us to be saved with the shedding of the blood of Christ. Just as in the Old Testament there had to blood shed for the remission of sin, so was Jesus that sacrifice for us and His blood cleanses us of our sin which helps us understand the power of God. With His blood, He has saved us, and by His power He has raised us with Him to eternal life.