Did Christ have to die in order to forgive us? Did He not have the authority to forgive sins before He even approached the cross? The answer to bother questions being: Yes. Christ having the authority to forgive sins prior to his death on the cross does not however render His physical death unnecessary.
“Indeed, under the law almost everything is purified with blood, and without the shedding of blood there is no forgiveness of sins. Thus it was necessary for the copies of the heavenly things to be purified with these rites, but the heavenly things themselves with better sacrifices than these. For Christ has entered, not into holy places made with hands, which are copies of the true things, but into heaven itself, now to appear in the presence of God on our behalf.”
The remission of sins, and adoption as heirs of Christ is impossible without the shedding of blood. This of course does not reference a simple time when blood flows, but the full life blood of a creature being drained for a propitiation. Likewise, Christ would be offered up in this manner to uphold the adoption of those whom I might call out as sons and daughters.
Though why must death be in place? Why must death be the rightful payment for sin? Simply put: If Christ is the source of life, and the light than to walk apart from Him is to walk in sin and death.
“Therefore, just as sin came into the world through one man, and death through sin, and so death spread to all men because all sinned— for sin indeed was in the world before the law was given, but sin is not counted where there is no law. Yet death reigned from Adam to Moses, even over those whose sinning was not like the transgression of Adam, who was a type of the one who was to come.”
Since all men have sinned and therefore our natural wage which we have earned has spread to us, that being death, we all must die in the end. Not a mere physical death, but an ever present spiritual death. A spiritual, physical, and mental death which clouds our judgement, making the things of the Lord seem as foolishness to us as we walked apart from Christ and in the darkness.
Since we ourselves walk through this death, in order to be the sacrifice for our sins, Christ would endure the same manner of wrath which we would naturally have inherited, that being one both of a spiritual nature and a physical nature. As the Father cast upon the Son the wrath which has been accrued by every sinner who would cry out to the Lord and accept Him as savior, Christ suffered the punishment which would ensure the efficacy of His forgiveness. As He gave up the ghost and His body finally died this was the final promise, as three days later He returned, fully alive, fully God, and fully Man. As He suffered the physical death which would be our naturally earned place, He took the final punishment, and once having conquered this He would have absolute authority to say that death has no sting, that our physical death is only a promise of what is to come for us as we are raised again with Him.
“saying, “Father, if you are willing, remove this cup from me. Nevertheless, not my will, but yours, be done.””
If there was any other way to have done what was to come, it would have been done in that way. Christ did not just die because the Romans crucified Him, but because He chose death.
“Yet it was the will of the LORD to crush him; he has put him to grief; when his soul makes an offering for guilt, he shall see his offspring; he shall prolong his days; the will of the LORD shall prosper in his hand.”
“when his soul makes an offering for guilt, he shall see his offspring” This would state that upon the event in which the Suffering Servant has put His soul as an offering then He would see His offspring. Death being the final offering, thus allowing us to become Children of God.
Yet, still He forgave sins before the cross.
“even as he chose us in him before the foundation of the world, that we should be holy and blameless before him. In love he predestined us for adoption as sons through Jesus Christ, according to the purpose of his will, to the praise of his glorious grace, with which he has blessed us in the Beloved.”
Christ had the foreknowledge to choose us before the foundation of the world, meaning he would have the foreknowledge to allocate the punishment of sins upon Himself before the crucifixion.