Our salvation could not have been effected by decree, no, not by even Divine decree. Death was necessary. Someone had to die.
"Christ died" (Romans 5:6).
Literally, "life" died - "I am... the life" (John 14:6). "Ye killed the Prince of life" declared the Apostle Peter to his generation, and to all generations of the sons and daughters of Adam who are complicit in the death of the Lord Jesus (Acts 3:13-14). For our sakes, the Savior entered into a reality that was completely foreign to His nature, being, and eternal existence. Indeed, it is one thing for sinful, fallen beings such as ourselves to die. It is a terrible thing, and tears beyond number stain the myriad faces of a race that has longing for eternity in its heart, but the ravages of time's decay in its body. "They die, and return to their dust" (Psalm 104:29). It is another thing, however, for One whose very essence is life to experience death.
There is little, and perhaps nothing we can write or think or say about this. We have no frame of reference for such a contradiction of soul and being. By definition, it should be impossible for eternal life to die. This nevertheless happened in the spirit, soul, and body of the Lamb of God. Our Lord was "made to be sin" for us, and then suffered the consequences of sin (II Corinthians 5:21). Perfect righteousness became sin. Again, there is no way we think thoughts, feel feelings, or use words for such a horror. The Lord Jesus became what He was not so that we might become what we were not, and "None of the ransomed ever knew how deep were the waters crossed, nor how dark was the night that our Lord passed through 'ere He found His sheep that was lost" ("The Ninety and Nine" - Elisabeth Cleophane).
We cannot know. Such recognition may be the brightest illumination that can shine within our hearts. We do well to often consider this Light that "shineth in darkness" (John 1:7). It will draw us as near as possible to awareness of a sacrifice far greater than mind, tongue, or pen will ever tell. Most of all, it will fuel and fan the flame of love in our hearts for the glorious One who loves us in a measure far greater than mind, tongue, or pen will ever tell. May it become personal for all of us that Life died in a mystery of contradiction and agony infinitely beyond anything we will ever know.
"He is... a man of sorrows, and acquainted with grief."