What did Christ do to pay for sin and open heaven for believers?

Les explains that the work of Christ on the cross settled everything needed for the sinner: He has paid the sin debt, He has suffered our punishment, and He has opened the windows of heaven if we'll just believe it, even though it happened 2,000 years ago. Because of this, the preaching of the cross is to them that perish foolishness, but unto us who are saved it is the power of God. Les stresses that salvation has to be an exercise of the sovereign power of an Almighty God, which is why man cannot work for his salvation — all man has is physical strength, but only God can bring about the salvation of the spiritual. He contrasts this with the Jews who require a sign and the Greeks who seek after wisdom, saying Paul bothers with neither signs nor a new philosophy, but preaches Christ crucified — to the Jews a stumbling block and to the Greeks foolishness, yet unto them who are called, both Jews and Greeks, Christ the power of God and the wisdom of God.