What did Christ do on the Cross? 

“Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed.” (1 Peter 2:24)

Here the holy Apostle  explains our Lord's work on the Cross. Jesus Christ voluntarily choose to die on the cross in order to cause our sins to die. The idea that he was sent to the cross by his Father in order to be punished in lieu of our being punished for our sins is a preposterous one, which the humble fisherman refutes magnificently here. 

Look closely at what he says: our Lord  “bare our sins in his own body”, that is, all of mankind's weaknesses, and predilection to sin, which made it impossible for us to attain unto the righteousness of God, in his own very human body. 

This act of  “baring our sins” is also stated in the parable of the good Samaritan. When the man, representing all of humanity was lying half dead on the road, Christ, our good Samaritan, attended to his wounds (all of which were because of our sins and our inability to keep from sinning) with oil and wine, and then put him on his beast and took him to an inn (church) for further recuperation. The beast represents the incarnation of the Son of God, who became man precisely to “bare our sins in his own body” and bring about our healing.

How did he heal us? As a man, he conquered sin; one could say he was “dead to sins”. As the God-man, when he “bare our sins in his own body on the tree”, He passed on to us the ability to also be “dead to sins” and taught us the way, and took care that his successors, the Holy Apostles, innkeepers, would be equipped to continue  living and teaching and passing on this way.   

His ministry was one of healing, not of forestalling  judgment and placating his Father. He and His Father, Who are one, were of one mind on His life's mission,  to teach us the way, and empower us to follow it, so that we, “being dead to sins, should live unto righteousness”

How wretched and lamentable we would be if our Lord only forgave our sins on the cross! Even if we are forgiven “seventy times seven” times, we would still be sinners, and sin causes great pain to our soul. The Lord came to forgive, and to heal. Forgiveness without healing is clearly not enough, because only the “pure in heart” will see God, and a forgiven sinner is still a sinner, and because of his impure nature, unable to be with God. The Lord forgave his disciples, and yet, when they were in the presence of the uncreated light on Mount Tabor, they could not bear it, because they had not become pure in heart. Only the healing of the soul, accomplished by our grace aided attempts to follow the commandments, will allow us to gaze upon the beauty of God without pain. 

Our Lord's work on the cross can be considered to be “central” to His mission in that it demarcated the two portions of his work,  His teaching and accomplishment of the way of life before his death,  and after his human death,  His shattering of the gates of Hell and subsequent ascension into heaven, which completed his healing of our very nature. With the sending of the Holy Spirit, we would have all that we need to be able to live righteously, and be “dead to sins, (and) should live unto righteousness.”

1 Peter 2:21-3:9  For even hereunto were ye called: because Christ also suffered for us, leaving us an example, that ye should follow his steps: Who did no sin, neither was guile found in his mouth: Who, when he was reviled, reviled not again; when he suffered, he threatened not; but committed himself to him that judgeth righteously: Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed. For ye were as sheep going astray; but are now returned unto the Shepherd and Bishop of your souls. Likewise, ye wives, be in subjection to your own husbands; that, if any obey not the word, they also may without the word be won by the conversation of the wives; While they behold your chaste conversation coupled with fear. Whose adorning let it not be that outward adorning of plaiting the hair, and of wearing of gold, or of putting on of apparel; But let it be the hidden man of the heart, in that which is not corruptible, even the ornament of a meek and quiet spirit, which is in the sight of God of great price. For after this manner in the old time the holy women also, who trusted in God, adorned themselves, being in subjection unto their own husbands: Even as Sara obeyed Abraham, calling him lord: whose daughters ye are, as long as ye do well, and are not afraid with any amazement. Likewise, ye husbands, dwell with them according to knowledge, giving honour unto the wife, as unto the weaker vessel, and as being heirs together of the grace of life; that your prayers be not hindered. Finally, be ye all of one mind, having compassion one of another, love as brethren, be pitiful, be courteous: Not rendering evil for evil, or railing for railing: but contrariwise blessing; knowing that ye are thereunto called, that ye should inherit a blessing.