John Gill Commentary Psalms 22:31

"They shall come and shall declare his righteousness Unto a people that shall be born, that he hath done it." — Psalms 22:31 (ASV)

They shall come
One generation after another; there shall always be a succession of regenerate persons, who shall come to Christ, and to his churches; and a succession of Gospel ministers among them, who shall come forth, being sent and qualified by Christ;

and shall declare his righteousness ,
either the faithfulness of God, in fulfilling his promises; especially those which respect the mission of Christ, and salvation by him, as Zacharias did, (Luke 1:68–73) ; or rather the righteousness of Christ, which is revealed in the Gospel, and makes a most considerable part of the declaration of it, and is published by Gospel ministers in all ages, as the only justifying righteousness before God: and that

unto a people that shall be born ;
in successive generations; that shall be brought upon the stage of time and life; or that shall be born again; for to such only, in a spiritual and saving way, is the righteousness of Christ declared, revealed, and applied, by the blessed Spirit, through the ministry of the word: it is added,

that he has done [this] ;
wrought this righteousness; so Jarchi; that is, is the author of it; is become the end of the law for it; has finished it, and brought it in; or else all the great things spoken of in this psalm, relating to the Messiah, his sufferings, death, and resurrection, and the calling of the Gentiles; all which are the Lord's doings, and are what is declared in the Gospel: the Targum is, "the miracles which he has done"; the Septuagint version, and those that follow it, connect this clause with the preceding thus, "to a people that shall be born, whom the Lord has made"; made them his people, created them in Christ, and formed them for himself.