33 Deliver us, O Lord our God, and gather us from among the nations (other copies read, “from the heathen”); that we may give thanks unto Your holy Name, and make our boast of Your praise. Then he has briefly added this very praise, “Blessed be the Lord God of Israel from everlasting, and world without end”: by which we understand from everlasting to everlasting; because He shall be praised without end by those of whom it is said, “Blessed are they that dwell in Your house: they will be always praising You.” This is the perfection of the Body of Christ on the third day, when the devils had been cast out, and cures perfected, even unto the immortality of the body itself, the everlasting reign of those who perfectly praise Him, because they perfectly love Him; and perfectly love Him, because they behold Him face to face.
For then shall be completed the prayer at the commencement of this Psalm: “Remember us, O Lord, according to the favour that You bear unto Your people,” etc. For from the Gentiles He does not gather only the lost sheep of the house of Israel, but also those which do not belong to that fold; so that there is one flock, as is said, and one Shepherd. But when the Jews suppose that that prophecy belongs to their visible kingdom, because they know not how to rejoice in the hope of good things unseen, they are about to rush into the snares of him, of whom the Lord says, “I have come in My Father's Name, and you receive Me not: if another shall come in his own name, him you will receive.” Of whom the Apostle Paul says: “that Man of Sin shall be revealed, the son of perdition,” etc.
And a little after he says, “Then shall that Wicked be revealed, whom the Lord shall consume with the Spirit of His mouth, and shall destroy with the brightness of His coming,” etc....Through that Apostate, through him who exalts himself above all that is called God, or that is worshipped, it seems to me, that the carnal people of Israel will suppose that prophecy to be fulfilled, where it is said, “Deliver us, O Lord, and gather us from among the heathen;” that under His guidance, before the eyes of their visible enemies, who had visibly taken them captive, they are to have visible glory.
Thus they will believe a lie, because they have not received the love of truth, that they might love not carnal, but spiritual blessings....For Christ had other sheep that were not of this fold: but the devil and his angels had taken captive all those sheep, both among the Israelites and the Gentiles. The power, therefore, of the devil having been cast out of them, in the sight of the evil spirits who had taken them captive, their cry in this prophecy is, that they may be saved and perfected for evermore: “Deliver us, O Lord our God, and gather us from among the heathen.”
Not, as the Jews imagine it, fulfilled through Antichrist, but through our Lord Christ coming in the name of His Father, “Day from day, His salvation;” of whom it is here said, “O visit us in Your salvation! And let all the people say,” the predestined people of the circumcision and of the uncircumcision, a holy race, an adopted people, “So be it! So be it!”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)