4 He then adds: “After this, Jesus knowing that all things were now accomplished, that the scripture might be fulfilled, says, I thirst. Now there was set a vessel full of vinegar: and they filled a sponge with vinegar, and fixed it upon hyssop, and put it to His mouth. When Jesus therefore had received the vinegar, He said, It is finished: and He bowed His head, and gave up the ghost.” Who has the power of so adjusting what he does, as this Man had of arranging all that He suffered?
But this Man was the Mediator between God and men; the Man of whom we read in prophecy, He is man also, and who shall acknowledge Him? For the men who did such things acknowledged not this Man as God. For He who was manifest as man, was hid as God: He who was manifest suffered all these things, and He Himself also, who was hid, arranged them all. He saw, therefore, that all was accomplished that required to be done before He received the vinegar, and gave up the ghost; and that this also might be accomplished which the scripture had foretold, “And in my thirst they gave me vinegar to drink,” He said, “I thirst:” as if it were, One thing still you have failed to do, give me what you are.
For the Jews were themselves the vinegar, degenerated as they were from the wine of the patriarchs and prophets; and filled like a full vessel with the wickedness of this world, with hearts like a sponge, deceitful in the formation of its cavernous and tortuous recesses. But the hyssop, whereon they placed the sponge filled with vinegar, being a lowly herb, and purging the heart, we fitly take for the humility of Christ Himself; which they thus enclosed, and imagined they had completely ensnared.
Hence we have it said in the psalm, “You shall purge me with hyssop, and I shall be cleansed.” For it is by Christ's humility that we are cleansed; because, had He not humbled Himself, and became obedient unto the death of the cross, His blood certainly would not have been shed for the remission of sins, or, in other words, for our cleansing.
Source: Tractates on the Gospel of John (New Advent)