What are the specific versus that support the prophesy of Jesus' side being pierced on the cross?
The usual reference for what we currently have in the Biblical Canon is from Zechariah 12:10. From the KJV, emphasis added:
And I will pour upon the house of David, and upon the inhabitants of Jerusalem, the spirit of grace and of supplications: and they shall look upon me whom they have pierced, and they shall mourn for him, as one mourneth for his only son, and shall be in bitterness for him, as one that is in bitterness for his firstborn.
Jesus was pierced on His side after He had died and none of His bones were broken.
Therefore, because it was the Preparation Day, that the bodies should not remain on the cross on the Sabbath (for that Sabbath was a high day), the Jews asked Pilate that their legs might be broken, and that they might be taken away. 32 Then the soldiers came and broke the legs of the first and of the other who was crucified with Him. 33 But when they came to Jesus and saw that He was already dead, they did not break His legs. 34 But one of the soldiers pierced His side with a spear, and immediately blood and water came out. 35 And he who has seen has testified, and his testimony is true; and he knows that he is telling the truth, so that you may believe. 36 For these things were done that the Scripture should be fulfilled, “Not one of His bones shall be broken.”[f] 37 And again another Scripture says, “They shall look on Him whom they pierced.”[g]
The Scriptures had foretold that He would be pierced,
“And I will pour on the house of David and on the inhabitants of Jerusalem the Spirit of grace and supplication; then they will look on Me whom they pierced. Yes, they will mourn for Him as one mourns for his only son, and grieve for Him as one grieves for a firstborn.
and that His bones would not be broken.
He keepeth all his bones: not one of them is broken.
This is important because the Jesus is the Lamb of God, as John the Baptist said,
The next day John seeth Jesus coming unto him, and saith, Behold the Lamb of God, which taketh away the sin of the world.
and He was the fulfillment of all the symbols of the Old Testament. The lambs that were sacrificed were to be perfect and their bones were not to be broken as they represented the Son of God who would come to die for us.
In one house it shall be eaten; you shall not carry any of the flesh outside the house, nor shall you break one of its bones.