Think of it. In order for God to atone for man's sin, someone had to subject Himself to death. Yet only one who had unlimited ability to atone for sin could do that, only a perfect man. He had to have unlimited ability to atone, because He would be shedding His blood for all humankind. He had to be perfect because God accepts only unblemished sacrifices. Who could do that? Only God. And God the Son shed His own blood for us (Acts 20:28) (Josh McDowell and Bart Larson).