Consequently it must be said that all the aforesaid words belong to the substance of the form; but that by the first words, "This is the chalice of My blood," the change of the wine into blood is denoted, as explained above (A. 2) in the form for the consecration of the bread; but by the words which come after is shown the power of the blood shed in the Passion, which power works in this sacrament, and is ordained for three purposes. First and principally for securing our eternal heritage, according to Heb. 10:19: "Having confidence in the entering into the holies by the blood of Christ"; and in order to denote this, we say, "of the New and Eternal Testament." Secondly, for justifying by grace, which is by faith according to Rom. 3:25, 26: "Whom God hath proposed to be a propitiation, through faith in His blood . . . that He Himself may be just, and the justifier of him who is of the faith of Jesus Christ": and on this account we add, "The Mystery of Faith." Thirdly, for removing sins which are the impediments to both of these things, according to Heb. 9:14: "The blood of Christ . . . shall cleanse our conscience from dead works," that is, from sins; and on this account, we say, "which shall be shed for you and for many unto the forgiveness of sins."
Reply Obj. 1: The expression "This is the chalice of My blood" is a figure of speech, which can be understood in two ways. First, as a figure of metonymy; because the container is put for the contained, so that the meaning is: "This is My blood contained in the chalice"; of which mention is now made, because Christ's blood is consecrated in this sacrament, inasmuch as it is the drink of the faithful, which is not implied under the notion of blood; consequently this had to be denoted by the vessel adapted for such usage.
Secondly, it can be taken by way of metaphor, so that Christ's Passion is understood by the chalice by way of comparison, because, like a cup, it inebriates, according to Lam. 3:15: "He hath filled me with bitterness, he hath inebriated me with wormwood": hence our Lord Himself spoke of His Passion as a chalice, when He said (Matt. 26:39): "Let this chalice pass away from Me": so that the meaning is: "This is the chalice of My Passion." This is denoted by the blood being consecrated apart from the body; because it was by the Passion that the blood was separated from the body.
Reply Obj. 2: As was said above (ad 1; Q. 76, A. 2, ad 1), the blood consecrated apart expressly represents Christ's Passion, and therefore mention is made of the fruits of the Passion in the consecration of the blood rather than in that of the body, since the body is the subject of the Passion. This is also pointed out in our Lord's saying, "which shall be delivered up for you," as if to say, "which shall undergo the Passion for you."
Reply Obj. 3: A testament is the disposal of a heritage. But God disposed of a heavenly heritage to men, to be bestowed through the virtue of the blood of Jesus Christ; because, according to Heb. 9:16: "Where there is a testament the death of the testator must of necessity come in." Now Christ's blood was exhibited to men in two ways. First of all in figure, and this belongs to the Old Testament; consequently the Apostle concludes (Heb. 9:16): "Whereupon neither was the first indeed dedicated without blood," which is evident from this, that as related in Ex. 24:7, 8, "when every" commandment of the law "had been read" by Moses, "he sprinkled all the people" saying: "This is the blood of the testament which the Lord hath enjoined unto you."
Secondly, it was shown in very truth; and this belongs to the New Testament. This is what the Apostle premises when he says (Rom. 9:15): "Therefore He is the Mediator of the New Testament, that by means of His death . . . they that are called may receive the promise of eternal inheritance." Consequently, we say here, "The blood of the New Testament," because it is shown now not in figure but in truth; and therefore we add, "which shall be shed for you." But the internal inspiration has its origin in the power of this blood, according as we are justified by Christ's Passion.
Reply Obj. 4: This Testament is a "new one" by reason of its showing forth: yet it is called "eternal" both on account of God's eternal pre-ordination, as well as on account of the eternal heritage which is prepared by this testament. Moreover, Christ's Person is eternal, in Whose blood this testament is appointed.
Reply Obj. 5: The word "mystery" is inserted, not in order to exclude reality, but to show that the reality is hidden, because Christ's blood is in this sacrament in a hidden manner, and His Passion was dimly foreshadowed in the Old Testament.
Reply Obj. 6: It is called the "Sacrament of Faith," as being an object of faith: because by faith alone do we hold the presence of Christ's blood in this sacrament. Moreover Christ's Passion justifies by faith. Baptism is called the "Sacrament of Faith" because it is a profession of faith. This is called the "Sacrament of Charity," as being figurative and effective thereof.
Reply Obj. 7: As stated above (ad 2), the blood consecrated apart represents Christ's blood more expressively; and therefore mention is made of Christ's Passion and its fruits, in the consecration of the blood rather than in that of the body.