When He so earnestly expressed His desire to eat the passover, He considered it His own feast; for it would have been unworthy of God to desire to partake of what was not His own. Then, having taken the bread and given it to His disciples, He made it His own body, by saying, “This is my body,” that is, the figure of my body. A figure, however, there could not have been, unless there were first a veritable body. An empty thing, or phantom, is incapable of a figure. If, however, (as Marcion might say,) He pretended the bread was His body, because He lacked the truth of bodily substance, it follows that He must have given bread for us. It would contribute very well to the support of Marcion’s theory of a phantom body, that bread should have been crucified! But why call His body bread, and not rather (some other edible thing, say) a melon, which Marcion must have had in lieu of a heart! He did not understand how ancient was this figure of the body of Christ, who said Himself by Jeremiah: “I was like a lamb or an ox that is brought to the slaughter, and I knew not that they devised a device against me, saying, Let us cast the tree upon His bread,” which means, of course, the cross upon His body. And thus, casting light, as He always did, upon the ancient prophecies, He declared plainly enough what He meant by the bread, when He called the bread His own body. He likewise, when mentioning the cup and making the new testament to be sealed “in His blood,” affirms the reality of His body. For no blood can belong to a body which is not a body of flesh.
…Much more clearly still does the book of Genesis foretell this, when (in the blessing of Judah, out of whose tribe Christ was to come according to the flesh) it even then delineated Christ in the person of that patriarch, saying, “He washed His garments in wine, and His clothes in the blood of grapes”—in His garments and clothes the prophecy pointed out his flesh, and His blood in the wine. Thus did He now consecrate His blood in wine, who then (by the patriarch) used the figure of wine to describe His blood.
Tertullian
The Five Books Against Marcion, Book IV
Chapter XL