V. 36. For these things were done that the scripture should be fulfilled, A bone of Him shall not be broken. V. 37. And again another scripture saith, They shall look on Him whom they pierced.
Both facts should be impressed upon the minds of the believers: that Christ truly died, and that this strange phenomenon took place at the piercing of His side. As one commentator has it: The blood that flowed from the side of Jesus was to serve for the washing of the sins of the whole world. It is the blood of reconciliation, the blood of God, wherewith He has cleansed all men from their sins.
"The blood which flows from the side of our Lord Jesus is the treasure of our redemption, the payment and atonement for our sins. For by His innocent suffering and death and through His holy, precious bloodshed on the cross, our dear Lord Jesus Christ has paid for all our guilt, eternal death, and damnation, in which we, because of our sins, are immersed. That same blood of Christ is our advocate with God, and without ceasing cries for us to God: Mercy, mercy; forgive, forgive; indulgence, indulgence; Father, Father! and thus earns for us God's grace, forgiveness of sins, righteousness, and salvation...
"Therefore the blood and the water which flowed from the side of our dear Lord Jesus Christ on the cross is our highest comfort. For therein consists our soul's salvation: in the blood is our redemption and satisfaction for our sins; in the water there is our daily cleansing and purging from sins. This we should learn well and thank God, our dear Lord, for His boundless love and goodness, and our faithful Savior Jesus Christ for His suffering and death, with all our hearts” (Luther, 8, 965, 969).
Incidentally, as the evangelist points out, there is another prophecy which was in part fulfilled on Calvary, in the piercing of the side of Christ, Ps. 22, 16. 17; Zech. 12, 10; Rev. 1, 7. The unbelieving Jews saw Him whose side was pierced hanging on the cross, and the fact should have recalled to their minds this prophecy of the Psalms and its import. The day will come when they will see the same Man against whom they vented their spite coming back to judge the quick and the dead; then their wailing and pleading for mercy will come too late.