His glory is great in thy salvation: honour and majesty hast thou laid upon him.

Wesley's Notes

21:5 Glory - His fame or renown. Salvation - By reason of those great and glorious deliverances which thou hast wrought both for him, and by him.

Matthew Henry's Concise Commentary

21:1-6 Happy the people whose king makes God's strength his confidence, and God's salvation his joy; who is pleased with all the advancements of God kingdom, and trusts God to support him in all he does for the service of it. All our blessings are blessings of goodness, and are owing, not to any merit of ours, but only to God's goodness. But when God's blessings come sooner, and prove richer than we imagine; when they are given before we prayed for them, before we were ready for them, nay, when we feared the contrary; then it may be truly said that he prevented, or went before us, with them. Nothing indeed prevented, or went before Christ, but to mankind never was any favour more preventing than our redemption by Christ. Thou hast made him to be a universal, everlasting blessing to the world, in whom the families of the earth are, and shall be blessed; and so thou hast made him exceeding glad with the countenance thou hast given to his undertaking, and to him in the prosecution of it. The Spirit of prophecy rises from what related to the king, to that which is peculiar to Christ; none other is blessed for ever, much less a blessing for ever.