Let’s read John 19:31-35 to get an understanding of this great event.  That says, “The Jews therefore, because it was the preparation, that the bodies should not remain upon the cross on the sabbath day, (for that sabbath day was an high day,) besought Pilate that their legs might be broken, and that they might be taken away. Then came the soldiers, and brake the legs of the first, and of the other which was crucified with him. But when they came to Jesus, and saw that he was dead already, they brake not his legs: But one of the soldiers with a spear pierced his side, and forthwith came there out blood and water. And he that saw it bare record, and his record is true: and he knoweth that he saith true, that ye might believe.”

These Jews, who refused and rejected Christ as their Messiah were so cautious to make sure that the bodies of the Lord Jesus and those crucified with Him were removed from their crosses before the approaching Sabbath Day.  What hypocrisy!  Death by crucifixion would normally take days.  It was slow and painful, typically due to suffocation, exposure, and dehydration.  These Jewish leaders asked Pilate to have their legs broken to expediate the process of death.  With the bones in their legs broken and giving no support, there would be great difficulty in breathing, resulting in suffocation very quickly. 

After breaking the legs of the two criminals, the soldiers discovered the Lord Jesus was already dead.  This was because He had already used His divine power and authority to dismiss His spirit from His body.  The Lord had said previously, “Therefore doth my Father love me, because I lay down my life, that I might take it again. No man taketh it from me, but I lay it down of myself. I have power to lay it down, and I have power to take it again. This commandment have I received of my Father.” (John 10:17-18).  After suffering for six hours on the cross, dying for lost sinners like you and me, we read in Luke 23:46, “And when Jesus had cried with a loud voice, he said, Father, into thy hands I commend my spirit: and having said thus, he gave up the ghost.” 

Having discovered the Lord was already dead, one soldier took his spear and stabbed the Lord in His side.  This wound was evidently large, for the Lord later said, “Then saith he to Thomas, Reach hither thy finger, and behold my hands; and REACH HITHER THY HAND, AND THRUST IT INTO MY SIDE: and be not faithless, but believing.” (John 20:27).  Why did this soldier stab the Lord like that?  I can only suppose it was to make certain that He was dead. 

“…and forthwith came thereout blood and water.”  Now, we get to your good and pointed question.  Why did blood and water come out from this wound in the Lord’s side?  The Lord’s body was up on a cross, with the soldier below, so the spear would have pierced His side at an upward angle and punctured His heart.  In the human body, water doesn’t separate from the blood until circulation stops, at which point it accumulates in the heart and lungs. Since both “blood and water came out” when one of the soldiers pierced His side with a spear, it shows that circulation had stopped.  This was striking evidence that the Lord Jesus was dead.  This creates an unquestionable fact that the Lord did indeed die, so that His resurrection cannot be doubted since He was truly dead, with clear evidence to support that fact.

This stabbing of the Lord also fulfilled two prophesies concerning Himself.  We read in John 19:36-37, “For these things were done, that the scripture should be fulfilled, A bone of him shall not be broken. And again another scripture saith, They shall look on him whom they pierced.”  I encourage you to read these two prophesies concerning the death of the Lord Jesus in Old Testament.  The first one refers to the Passover Lamb in Exodus 12:46 and Numbers 9:12. The second one is found in Zechariah 12:10 and Psalm 22:16.  (CC)  (694.6)