Bede the Venerable
Catena Aurea · Markusevangelium 14
And as they did eat, Jesus took bread, and blessed, and brake it, and gave to them, and said, Take, eat: this is my body. And he took the cup, and when he had given thanks, he gave it to them: and they all drank of it. And he said unto them, This is my blood of the new testament, which is shed for many. Verily I say unto you, I will drink no more of the fruit of the vine, until that day that I drink it new in the kingdom of God.
(ubi sup.) The wine of the Lord’s cup is mixed with water, because we should remain in Christ and Christ in us. For on the testimony of John, the waters are the people, and it is not lawful for any one to offer either wine alone, or water alone, lest such an oblation should mean that the head may be severed from the members, and either that Christ could suffer without love for our redemption, and that we can be saved or be offered to the Father without His Passion. (Apoc. 17:15) It goes on: And they all drank of it.