Darkness is simply the absence of light, but spiritual darkness is evil. Evil has a leader, who, up to this point in the Gospel of Matthew, has constantly been trying to get Jesus to sin and to disregard God's plan that He sacrifice Himself on the cross.

Why was God's plan for His own Son to die? God's biblical rule required blood sacrifice to eliminate sin. However, animal blood was not good enough. It had to be done over and over. Our own sinful blood was not good enough. Only the pure blood of Jesus could eliminate sin once and for all. When Jesus died and rose again, He conquered evil, He conquered sin, and He conquered the grave. Darkness could not hold Him down!