John 19:34

34 Instead, one of the soldiers pierced Jesus’ side with a spear, bringing a sudden flow of blood and water.

Read John 19:34 Using Other Translations

But one of the soldiers with a spear pierced his side, and forthwith came there out blood and water.
But one of the soldiers pierced his side with a spear, and at once there came out blood and water.
One of the soldiers, however, pierced his side with a spear, and immediately blood and water flowed out.

What does John 19:34 mean?

John Gill's Exposition of the Bible
John 19:34

But one of the soldiers
Whose name some pretend to say was Longinns, and so called from the spear with which he pierced Christ:

with a spear pierced his side;
his left side, where the heart lies; though the painters make this wound on the right, and the Arabic version of Erpenius, as cited by Dr. Lightfoot, adds the word "right" to make the miracle the greater: this the soldier did, partly out of spite to Christ, and partly to know whether he was really dead; and which was so ordered by divine providence, that it might beyond all doubt appear that he really died, and was not taken down alive from the cross; so that there might be no room to call in question the truth of his resurrection, when he should appear alive again:

and forthwith came there out blood and water;
this is accounted for in a natural way by the piercing of the "pericardium", which contains a small quantity of water about the heart, and which being pierced, a person, if alive, must inevitably die; but it seems rather to be something supernatural, from the asseverations the evangelist makes. This water and blood some make to signify baptism and the Lord's supper, which are both of Christ's appointing, and spring from him, and refer to his sufferings and death; rather they signify the blessings of sanctification and justification, the grace of the one being represented by water, as it frequently is in the Old and New Testament, and the other by blood, and both from Christ: that Christ was the antitype of the rock in the wilderness, the apostle assures us, in ( 1 Corinthians 10:4 ) and if the Jews are to be believed, he was so in this instance; Jonathan ben Uzziel, in his Targum on ( Numbers 20:11 ) says that

``Moses smote the rock twice, at the first time (amda tpyja) , "blood dropped out": and at the second time abundance of waters flowed out.''
The same is affirmed by others F8 elsewhere in much the same words and order.
FOOTNOTES:

F8 Shemot Rabba, sect. 3. fol. 94. 1. Zohar in Num. fol. 102. 4.
California - Do Not Sell My Personal Information  California - CCPA Notice