Matt 27:40...If thou be the Son of God, come down from the cross.
Matt 27:42...If he be the King of Israel, let him now come down from the cross, and we will believe him.
Jesus was mocked by humanity. He was ridiculed by the Pharisees yet there was no guile found in His mouth. He was "made" sin who knew no sin, that "we" might be made the righteousness of God in Him. He bore the punishment for sin in His fleshly body at Calvary yet His soul did not see corruption. He could have come down off the cross and proved that He had power to do so..but didn't. Jesus by the Grace of God tasted suffering and death so that you and I could be saved and redeemed from eternal separation from God. When Jesus suffered on the cross He tasted death for fallen man.
Heb 2:9-10...But we see Jesus, who was made a little lower than the angels for the suffering of death, crowned with glory and honour; that he by the grace of God should taste death for every man.
Christ tasted death for you and I. He could have came down off the cross because He had the power to do so...but didn't according to the plan of God. His compassion and mercy for fallen man can not be described in His suffering. His love for fallen man cannot be described as He hung on the cross in public shame. Did He have power to come down from the cross and prove He was God? Yes, but if He would have come down from the cross you and I would not have had any means of redemption. Redemption flows from Calvary. The Holy Spirit was given to humanity through the Church that was birthed at Calvary. If Jesus would have come down off the cross the Church wouldn't have been birthed. Mosaic Law would not have ceased and Grace would not have begun.
During the ninth hour(after darkness was over all the land) Jesus commended His Spirit into the hands of the Father and cried out, "It is finished"...and then He gave up the ghost. The son of God had power to come down off the cross but didn't so you and could be saved. Glory!