One of the effects of the fall of Adam on humanity was that they all be subject to death. Since Christ was perfectly holy and did not contract original sin, then how is it possible for him to die? Did he assume the temporal effects of sin, such as pain, sickness, death, etc., but not assume the cause of original sin (i.e. rebellion against God)? Or was there another process? I know this is a mystery and we don’t truly know what happened, but please help me get a better understanding. Thank you.
As you point out, the Paschal mystery is indeed a mystery. The specific mechanisms of it are beyond us. However, Scripture does give us clues:
We had all gone astray like sheep, all following our own way; But the LORD laid upon him the guilt of us all…My servant, the just one, shall justify the many, their iniquity he shall bear… Because he surrendered himself to death, was counted among the transgressors, bore the sins of many, and interceded for the transgressors. - Isaiah 53:6, 11, 12
For our sake he made him to be sin who did not know sin, so that we might become the righteousness of God in him. - 2 Cor 5:21
No one takes it from me, but I lay it down on my own. I have power to lay it down, and power to take it up again. - John 10:18
Essentially, on the cross Jesus takes on all the effects of sin without actually having sinned. In Old Testament sacrifices, the animal of sacrifice was unblemished but the priest would lay his hands on it to “pass on” the sins of the people to the animal (Lev 4:3, 23, 32). This is a kind of typology for what would come to fulfillment in Jesus. Jesus clearly did not die because He suffered from original sin, rather He *chose *to permit Himself to suffer its effect of suffering and death. He chose to suffer those effects without ever being guilty of sin.