Psalm 72:19 (ESV) … “Blessed be his glorious name forever; may the whole earth be filled with his glory! Amen and Amen!”
And blessed be his glorious name for ever. The name by which he is known,—referring perhaps particularly to his name Jehovah. Still the prayer would be, that all the names by which he is known, all by which he has revealed himself, might be regarded with veneration always and everywhere.
And let the whole earth be filled with his glory. With the knowledge of himself; with the manifestations of his presence; with the influences of his religion. Comp. Num. 14:21. This prayer was peculiarly appropriate at the close of a psalm designed to celebrate the glorious reign of the Messiah. Under that reign the earth will be, in fact, filled with the glory of God; the world will be a world of glory. Assuredly all who love God, and who love mankind, all who desire that God may be honoured, and that the world may be blessed and happy, will unite in this fervent prayer, and re-echo the hearty “Amen and amen” of the psalmist.
Amen, and amen. So be it. Let this occur. Let this time come. The expression is doubled to denote intensity of feeling. It is the going out of a heart full of desire that this might be so.
David intended this prayer in another sense. “Let the whole earth be filled with his glory; Amen, and Amen;” not as Creator, but as a moral Governor, and a Ruler. It is as Governor that we have revolted from God and done dishonor to him; it is as our Master, our Ruler, our Judge, that we have done despite to his glory, and have trampled on his crown. It is, therefore, in this respect that David wished that the whole earth might be filled with God’s glory. He desired that every idol temple might be cast down—that the name of Jehovah might be sung by every lip, that he in his person might be loved by every heart, and be for ever adored as “God over all blessed for ever.” A foolish wish, say you, for it never can be accomplished. Surely the day will never come when hoary systems of superstition shall die. What! shall colossal systems of infidelity and of idolatry totter to their fall? They have resisted the battering-ram for many a year; and yet shall they pass away, and shall God’s kingdom come, and his will be done on earth, even as it is in heaven? Nay, it is no day dream of a boy; it is no wish of the enthusiast. Mark who uttered that prayer, and where he was when he uttered it. It was the prayer of a dying king; it was the prayer of a holy man of God, whose eyes were just then lighted up with brightness in view of the celestial city, as he stood on the mighty Pisgah, “and viewed the landscape o’er”—the prayer of the dying psalmist, when on the margin of his life he surveyed the ocean—the prayer of a mighty king, when he saw the scroll of prophecy unfolded before him for the last time, and was about to be ushered into the presence of his Maker. He uttered this as his last best wish and desire; and when he had uttered it he sank back in his bed, and said, “The prayers of David the son of Jesse are ended.” It was his last prayer: “Let the whole earth be filled with his glory; Amen, and Amen.”
 Barnes, A. (1870–1872). Notes on the Old Testament: Psalms (Vol. 2, pp. 250–251). Blackie & Son.  Spurgeon, C. H. (1857). David’s Dying Prayer. In The New Park Street Pulpit Sermons (Vol. 3, p. 178). Passmore & Alabaster.