Augustine of Hippo
Catena Aurea · Johannesevangelium 19
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. 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. Besought Pilate that their legs might be broken.
(Tr. cxx.) The Evangelist has expressed himself cautiously; not struck, or wounded, but opened His side: (ἔνυξε, aperuit V.) whereby was opened the gate of life, from whence the sacraments of the Church flowed, without which we cannot enter into that life which is the true life: And forthwith came thereout blood and water. That blood was shed for the remission of sins, that water tempers the cup of salvation. This it was which was prefigured when Noah was commanded to make a door in the side of the ark, by which the animals that were not to perish by the deluge entered; which animals prefigured the Church. To shadow forth this, the woman was made out of the side of the sleeping man; for this second Adam bowed His head, and slept on the cross, that out of that which came therefrom, there might be formed a wife for Him. O death, by which the dead are quickened, what can be purer than that blood, what more salutary than that wound!