What is the preaching of the cross to the perishing versus the saved?

Les explains that Christ has paid the sin debt, suffered our punishment, and opened the windows of heaven for those who believe, even though it happened 2,000 years ago. Therefore the preaching of the cross divides: to them that perish it is foolishness, but to us who are saved it is the power of God. Salvation must be an exercise of the sovereign power of Almighty God, which is why man cannot work for it. Man has only physical strength, but only God can bring about the salvation of the spiritual. Les also notes that the Jews require a sign and the Greeks seek wisdom, but Paul refuses to pursue either signs or a new philosophy. Instead, they preach Christ crucified: to the Jews a stumbling block, to the Greeks foolishness, but to the called, both Jews and Greeks, Christ is the power of God and the wisdom of God.