Objection 1. It seems that Christ did not merit to be exalted on account of His Passion. For eminence of rank belongs to God alone, just as knowledge of truth, according to Psalm 112:4: "The Lord is high above all nations, and His glory above the heavens." But Christ as man had the knowledge of all truth, not on account of any preceding merit, but from the very union of God and man, according to John 1:14: "We saw His glory... as it were of the only-Begotten of the Father, full of grace and of truth." Therefore neither had He exaltation from the merit of the Passion but from the union alone.
Objection 2. Further, Christ merited for Himself from the first instant of His conception, as stated above (Question 34, Article 3). But His love was no greater during the Passion than before. Therefore, since charity is the principle of merit, it seems that He did not merit exaltation from the Passion more than before.
Objection 3. Further, the glory of the body comes from the glory of the soul, as Augustine says (Ep. ad Dioscor.). But by His Passion Christ did not merit exaltation as to the glory of His soul, because His soul was beatified from the first instant of His conception. Therefore neither did He merit exaltation, as to the glory of His body, from the Passion.
On the contrary, It is written (Philippians 2:8): "He became obedient unto death, even the death of the cross; for which cause God also exalted Him."
I answer that, Merit implies a certain equality of justice: hence the Apostle says (Romans 4:4): "Now to him that worketh, the reward is reckoned according to debt." But when anyone by reason of his unjust will ascribes to himself something beyond his due, it is only just that he be deprived of something else which is his due; thus, "when a man steals a sheep he shall pay back four" (Exodus 22:1). And he is said to deserve it, inasmuch as his unjust will is chastised thereby. So likewise when any man through his just will has stripped himself of what he ought to have, he deserves that something further be granted to him as the reward of his just will. And hence it is written (Luke 14:11): "He that humbleth himself shall be exalted."
Now in His Passion Christ humbled Himself beneath His dignity in four respects. In the first place as to His Passion and death, to which He was not bound; secondly, as to the place, since His body was laid in a sepulchre and His soul in hell; thirdly, as to the shame and mockeries He endured; fourthly, as to His being delivered up to man's power, as He Himself said to Pilate (John 19:11): "Thou shouldst not have any power against Me, unless it were given thee from above." And, consequently, He merited a four-fold exaltation from His Passion. First of all, as to His glorious Resurrection: hence it is written (Psalm 138:1): "Thou hast known my sitting down"--that is, the lowliness of My Passion--"and My rising up." Secondly, as to His ascension into heaven: hence it is written (Ephesians 4:9): "Now that He ascended, what is it, but because He also descended first into the lower parts of the earth? He that descended is the same also that ascended above all the heavens." Thirdly, as to the sitting on the right hand of the Father and the showing forth of His Godhead, according to Isaiah 52:13: "He shall be exalted and extolled, and shall be exceeding high: as many have been astonished at him, so shall His visage be inglorious among men." Moreover (Philippians 2:8) it is written: "He humbled Himself, becoming obedient unto death, even to the death of the cross: for which cause also God hath exalted Him, and hath given Him a name which is above all names"--that is to say, so that He shall be hailed as God by all; and all shall pay Him homage as God. And this is expressed in what follows: "That in the name of Jesus every knee should bow, of those that are in heaven, on earth, and under the earth." Fourthly, as to His judiciary power: for it is written (Job 36:17): "Thy cause hath been judged as that of the wicked cause and judgment Thou shalt recover."
Reply to Objection 1. The source of meriting comes of the soul, while the body is the instrument of the meritorious work. And consequently the perfection of Christ's soul, which was the source of meriting, ought not to be acquired in Him by merit, like the perfection of the body, which was the subject of suffering, and was thereby the instrument of His merit.
Reply to Objection 2. Christ by His previous merits did merit exaltation on behalf of His soul, whose will was animated with charity and the other virtues; but in the Passion He merited His exaltation by way of recompense even on behalf of His body: since it is only just that the body, which from charity was subjected to the Passion, should receive recompense in glory.
Reply to Objection 3. It was owing to a special dispensation in Christ that before the Passion the glory of His soul did not shine out in His body, in order that He might procure His bodily glory with greater honor, when He had merited it by His Passion. But it was not beseeming for the glory of His soul to be postponed, since the soul was united immediately with the Word; hence it was beseeming that its glory should be filled by the Word Himself. But the body was united with the Word through the soul.
Source: Summa Theologica (New Advent)