22:20 Likewise also the cup after supper, saying, This {g} cup [is] {h} the new testament in my blood, which is shed for you.
(g) Here is a double use of metonymy: for first, the vessel is taken for that which is contained in the vessel, as the cup is spoken of for the wine which is within the cup. Second, the wine is called the covenant or testament, whereas in reality it is but the sign of the testament, or rather of the blood of Christ by which the testament was made: neither is it a vain sign, although it is not the same as the thing that it represents.
(h) This word the shows the excellency of the testament, and corresponds to Jer 31:31 where the new testament is promised.
22:14-20 When the hour was come. There are four accounts of the institution of the Lord's Supper: Mt 26:26-30 Mr 14:22-25 1Co 11:23-25. See notes on Matthew.
22:20 This cup is the New Testament - Here is an undeniable figure, whereby the cup is put for the wine in the cup. And this is called, The New Testament in Christ's blood, which could not possibly mean, that it was the New Testament itself, but only the seal of it, and the sign of that blood which was shed to confirm it.
22:19,20 The Lord's supper is a sign or memorial of Christ already come, who by dying delivered us; his death is in special manner set before us in that ordinance, by which we are reminded of it. The breaking of Christ's body as a sacrifice for us, is therein brought to our remembrance by the breaking of bread. Nothing can be more nourishing and satisfying to the soul, than the doctrine of Christ's making atonement for sin, and the assurance of an interest in that atonement. Therefore we do this in rememberance of what He did for us, when he died for us; and for a memorial of what we do, in joining ourselves to him in an everlasting covenant. The shedding of Christ's blood, by which the atonement was made, is represented by the wine in the cup.