O Lord God of hosts - See the notes at Isaiah 1:9; Psalm 24:10. God, commanding the armies of heaven; leading forth the stars; controlling all forces - all powers.
Who is a strong Lord like unto thee? - The original word here rendered "Lord" is יה Yâhh, or Jah. This is one of the few places where that word occurs, except in the compounding of words. It is an abbreviation of the name Yahweh, and has the same signification. See the notes at Psalm 68:4. The meaning is, that there was no one who in respect to power could be compared with Yahweh.
Or to thy faithfulness round about thee? - Rather, "thy faithfulness is round about thee." That is, It attends thee at all times; it is always with thee; it is a part of thy very nature. To all round about thee, thou art faithful; wherever God is - and he is everywhere - there is faithfulness. He never changes; and people and angels may always trust in him. The psalmist then proceeds to illustrate the greatness of his power, and of his faithfulness, in the works of creation. The design of these illustrations, doubtless, is to keep before the mind the idea of the divine faithfulness as shown in the works of nature, and then to apply this to the covenant which had been made with David. The idea is, that he who is so faithful in nature will be the same in grace; that he who had shown such unchangeableness in the works of creation might be expected to show the like in respect to the promises which he had made.

O Lord God of hosts - Thou who hast all armies at thy command, and canst serve thyself by every part of thy creation, whether animate or inanimate.
Who is a strong Lord - See Psalm 89:6.
Thy faithfulness round about thee? - Or, more properly, thy faithfulness is round about thee. Thou still keepest thy promises in view. God's truth leads him to fulfill his promises: they stand round his throne as the faithful servants of an eastern monarch stand round their master, waiting for the moment of their dismission to perform his will.

O Lord God of hosts,.... Of all the hosts of heaven, the sun, moon, and stars, and of all the heavenly hosts of angels, of all the armies in heaven, and the inhabitants of the earth:
who is a strong Lord like unto thee? he is Jah, or Jehovah, and he alone is so, and is the most High in all the earth, Psalm 83:18 and there is none like him for his great power and strength, by which he has made the heavens and the earth, and upholds them in their being; and by which he has redeemed his people, plucked them out of the hands of sin and Satan, and preserves them safe to his kingdom and glory: see Job 40:9,
or to thy faithfulness round about thee; none so faithful as the Lord, none to be trusted as he, either angels or men; some understand it of the faithful ones that are about him, his trusty servants the angels, who stand round about him ready to do his will; or the glorified saints that are with him, the called, chosen, and faithful; see Psalm 103:19 or rather the words are to be read, "and thy faithfulness is round about thee"; and so the Targum,
"and thy truth (or faithfulness) surroundeth thee:''
look all around him, and his faithfulness is everywhere to be seen; to himself, and the perfections of his nature; to his Son, and agreements with him; and to his counsels of old, his purposes and decrees, and to his covenant and promises: he is as it were clothed with faithfulness, and it appears in all the dispensations of his providence and grace.

To illustrate His power and faithfulness examples are cited from history. His control of the sea (the most mighty and unstable object in nature), and of Egypt (Psalm 87:4), the first great foe of Israel (subjected to utter helplessness from pride and insolence), are specimens. At the same time, the whole frame of nature founded and sustained by Him, Tabor and Hermon for "east and west," and "north and south," together representing the whole world, declare the same truth as to His attributes.

Round thee - Like a girdle encompassing thee. It appears in all thy words and works.