I believe that it was the fact that He knew that His death could only come about when He Himself, while hanging on that cross, took upon His body the sins of the whole world. But now it was going to have to under go the degradation of becoming sin. He knew the kingdom principles involved. Death is necessary to put a covenant of redemption into effect. Spirit cannot die, only a body dies.
Bodies die only because of sin.
Christ had to become sin in order to physically die. At this point the sheer beauty and simplicity of the Word begins to shine forth. We then submit to them out of love, and they will work. God Himself followed His kingdom principles. We have now come full circle.