Synopsis of the Books of the Bible, by John Nelson Darby, [1857-62], at sacred-texts.com
Psalm 99, though simple in its character, embraces some important principles. Jehovah now reigns, not only in making manifest heavenly power, but in the establishment of that power as king upon the earth. He now sits between the cherubim as heretofore in Israel. He is great in Zion and high above all peoples. I have no doubt this word people (ammim), generally translated "people" in the Authorised Version, which confounds it with Israel, is used, not as goim (Psa 98:2 and often) in opposition with Israel and the knowledge of Jehovah, but for nations not Israel, but brought into relationship with Israel, and so with Jehovah Himself. Israel is called goi (Psalm 43) when judged and rejected. Further, the King (Messiah, but still Jehovah) loves judgment, and establishes equity, executing judgment and righteousness in Jacob. Thus Jehovah, the God of Jacob, was to be exalted, and in Jerusalem.
But another touching and important principle is then brought out: Israel had utterly failed, cast off Jehovah, rejected Messiah, was judged and cast off. But Jehovah had never given up His faithfulness and grace. Hence the Spirit turns back here to recognise the saints under the old covenant who had, through grace, been faithful (the remnant was always acknowledged; in one aspect we are it still, all children of Jerusalem the desolate, and waiting under discipline and government, only a Father's). Moses and Aaron among His priests, Samuel among those who called on His name, the true prophets with no office, whatever their measure these called on Jehovah, and He heard them. The relationship of faith was there. Jehovah answered them, but governed His people, taking vengeance of their inventions. So, at the end, whosoever shall call on the name of Jehovah shall be saved; but how surely are their inventions punished! These are the two hinges of all God's waysgrace and the ear of goodness to the cry of the meek and needy, and government as holy and true. So with us: only we have a Father's government (still God's) after salvation and adoption. Thus new-born Israel is identified with the faithful Israel of old. The child of Ruth and Boaz is a son born to Naomi. Mara is known no more.