John 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.
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