When the Lord shall build up Zion - The Septuagint, the Latin Vulgate, and Luther, vender this, “Because the Lord hath built up Zion.” This also is the most natural and correct translation of the Hebrew. The reference, however, may be to the future. The psalmist may throw himself into the future, and - standing there - he may describe things as they will appear then - as already done.
He shall appear in his glory - The idea is that the building up of Zion would be an occasion in which God would manifest his glory. In reference to the restoration of his people from bondage; in rebuilding Zion, then in ruins; in restoring the splendor of the place where he had been so long worshipped, he would display his true character as a God of glory, truth, power, and goodness. As applied to the church in general, this would mean that when God comes to revive religion, to visit his people, to recover them from their backslidings, to convert and save sinners, he appears in his appropriate character as the God of his people - as a glorious God. Then the perfections of his nature are most illustriously displayed; then he appears in his true character, as a God of mercy, grace, and salvation. There is no scene on earth where the character of God is more gloriously exhibited than in a revival of true religion.