2 The people of God, then, in this Psalm says, “O God, who shall be like You?”. Which I suppose to be more fitly taken of Christ, because, being made in the likeness of men, He was thought by those by whom He was despised to be comparable to other men: for He was even “reckoned among the unrighteous,” but for this purpose, that He might be judged. But when He shall come to judge, then shall be done what is here said, “O God, who is like You?” For if the Psalms did not use to speak to the Lord Christ, that too would not be spoken which not one of the faithful can doubt was spoken unto Christ. “Your throne, O God, is for ever and ever, a sceptre of righteousness is the sceptre of Your kingdom.” To him therefore also now it is said, “O God, who shall be like You?” For unto many You vouchsafed to be likened in Your humiliation, even so far as to the robbers that were crucified with You: but when in glory You shall come, “who shall be like You?”...
Source: The Enarrations, or Expositions, on the Psalms (New Advent)