Reply Obj. 1: Although Christ did not fall by sin, yet He fell by death, because as sin is a fall from righteousness, so death is a fall from life: hence the words of Mic. 7:8 can be taken as though spoken by Christ: "Rejoice not thou, my enemy, over me, because I am fallen: I shall rise again." Likewise, although Christ's body was not disintegrated by returning to dust, yet the separation of His soul and body was a kind of disintegration.
Reply Obj. 2: The Godhead was united with Christ's flesh after death by personal union, but not by natural union; thus the soul is united with the body as its form, so as to constitute human nature. Consequently, by the union of the body and soul, the body was uplifted to a higher condition of nature, but not to a higher personal state.
Reply Obj. 3: Christ's Passion wrought our salvation, properly speaking, by removing evils; but the Resurrection did so as the beginning and exemplar of all good things. _______________________
SECOND ARTICLE [III, Q. 53, Art. 2]
Whether It Was Fitting for Christ to Rise Again on the Third Day?
Objection 1: It would seem unfitting that Christ should have risen again on the third day. For the members ought to be in conformity with their head. But we who are His members do not rise from death on the third day, since our rising is put off until the end of the world. Therefore, it seems that Christ, who is our head, should not have risen on the third day, but that His Resurrection ought to have been deferred until the end of the world.
Obj. 2: Further, Peter said (Acts 2:24) that "it was impossible for Christ to be held fast by hell" and death. Therefore it seems that Christ's rising ought not to have been deferred until the third day, but that He ought to have risen at once on the same day; especially since the gloss quoted above (A. 1) says that "there is no profit in the shedding of Christ's blood, if He did not rise at once."
Obj. 3: The day seems to start with the rising of the sun, the presence of which causes the day. But Christ rose before sunrise: for it is related (John 20:1) that "Mary Magdalen cometh early, when it was yet dark, unto the sepulchre": but Christ was already risen, for it goes on to say: "And she saw the stone taken away from the sepulchre." Therefore Christ did not rise on the third day.
On the contrary, It is written (Matt. 20:19): "They shall deliver Him to the Gentiles to be mocked, and scourged, and crucified, and the third day He shall rise again."
I answer that, As stated above (A. 1) Christ's Resurrection was necessary for the instruction of our faith. But our faith regards Christ's Godhead and humanity, for it is not enough to believe the one without the other, as is evident from what has been said (Q. 36, A. 4; cf. II-II, Q. 2, AA. 7, 8). Consequently, in order that our faith in the truth of His Godhead might be confirmed it was necessary that He should rise speedily, and that His Resurrection should not be deferred until the end of the world. But to confirm our faith regarding the truth of His humanity and death, it was needful that there should be some interval between His death and rising. For if He had risen directly after death, it might seem that His death was not genuine and consequently neither would His Resurrection be true. But to establish the truth of Christ's death, it was enough for His rising to be deferred until the third day, for within that time some signs of life always appear in one who appears to be dead whereas he is alive.