Bless the Lord - The psalm began Psalm 103:1-2 with an exhortation to "bless the Lord." That exhortation was, however, then addressed by the psalmist to his own soul, and was especially founded on the benefits which he had himself received. The psalm closes also with an exhortation to "bless the Lord," yet on a much wider scale. The psalmist feels that there is not only occasion for him to do it, but that the reason for it extends to the whole universe. The meaning is, that God is worthy of universal praise; and all ranks of beings - all worlds - should join in that praise. Man, feeble, frail, dying, could not come up to the fullness of the praise required. Praise such as was appropriate to God - such as his perfections and works deserved - demanded loftier powers than those of man; the loftiest powers in the universe.
Ye his angels - All beings higher than man; beings around and before his throne.
That excel in strength - Margin, as in Hebrew, "mighty in strength," and therefore more "able" to offer adequate praise.
That do his commandments - Who perfectly obey his law, and who, therefore, can render more acceptable praise than can ever come from human lips.
Hearkening unto the voice of his word - Who always listen to his voice; who never are disobedient; and who can, therefore, approach him as holy beings, and more appropriately worship him.

Bless the Lord, ye his angels - Every person who has a sense of God's goodness to his soul feels his own powers inadequate to the praise which he ought to offer; and therefore naturally calls upon the holiest of men, and the supreme angels, to assist him in this work.
That excel in strength - Some take גברי כה gibborey coach the mighty in strength, for another class of the hierarchy, - they that do his commandments, hearkening to his words; and consider them to be that order of beings who are particularly employed in operations among and for the children of men; probably such as are called powers in the New Testament.

Bless the LORD, ye (m) his angels, that excel in strength, that do his commandments, hearkening unto the voice of his word.
(m) In that we, who naturally are slow to praise God, exhort the angels, who willingly do it, we stir up ourselves to consider our duty and wake from our sluggishness.

Bless the Lord, ye his angels,.... For their creation, being made by him; for their preservation, living, moving, and having their being in him; and for their happiness, in which they are continued, owing to their being chosen of God in Christ, and to their confirmation by Christ. These are always employed in the work of blessing and praising the Lord nor are they in the least backward to it, nor remiss it; nor does this address unto them suppose anything of this kind. The design of the psalmist is only to show how great and good the Lord is; that angels, the more excellent order of creatures, are under obligation to him, and are bound to praise him: and his further view is, to stir up himself and others to this work, from such a consideration, that such noble creatures are employed in the same, and who are further described:
that excel in strength; or, "are mighty in strength" (e); they are called mighty angels, 2-Thessalonians 1:7 an instance of the might and power of an angel see in 2-Kings 19:35. These, not having sinned, have lost nothing of their original strength and power, and therefore must greatly excel fallen man; who is become a very weak creature, and unable to do the will and work of God, which angels are, as follows:
that do his commandments; or "his word" (f); what he orders to be done: this they do readily and willingly, constantly, perfectly, and completely; see Matthew 6:10.
Hearkening to the voice of his word; they stand before the Lord, waiting his orders; listening with great attention to what he says, and then readily execute it. Or, "at hearing the voice of his word"; that is, as soon as they hear the voice of his word, or hear him speaking (g), immediately they apply themselves to the performance of it.
(e) "fortes robore", Pagninus, Montanus; "valentissimi robore", Junius & Tremellius. (f) "verbum ejus", Pagninus, Montanus, Junius & Tremellius, Piscator. (g) So Muis.

do his commandments . . . word--or, literally, "so as to hearken," &c., that is, their acts of obedience are prompt, so that they are ever ready to hear, and know, and follow implicitly His declared will (compare Deuteronomy 26:17; Luke 1:19).