“But one of the soldiers with a spear pierced his side, and forthwith came there out blood and water.”
King James Version (KJV)
19:34 Forthwith there came out blood and water - It was strange, seeing he was dead, that blood should come out; more strange, that water also; and most strange of all, that both should come out immediately, at one time, and yet distinctly. It was pure and true water, as well as pure and true blood. The asseveration of the beholder and testifier of it, shows both the truth and greatness of the miracle and mystery.
Joh 19:34 Pierced his side. Finding him lifeless, the soldiers did not break his legs, but to make sure of death thrust a spear into his side. Came there out blood and water. The water, with clots of blood, can be accounted for only the previous rupture of the heart and the flow of blood into the pericardium, or outer sack of the heart, where it would separate very rapidly into water and clots of blood. Hence, it seems certain that the immediate physical cause of the death of Christ was rupture of the heart.