Who shall express. This verse is susceptible of two interpretations; for if you read it in connection with the one immediately following, the sense will be, that all men are not alike equal to the task of praising God, because the ungodly and the wicked do nothing else than profane his holy name with their unclean lips; as it is said in the fiftieth psalm: "But unto the wicked God saith, What hast thou to do to declare my statutes, or that thou shouldest take my covenant in thy mouth?" And hence to this sentence the following clause should have been annexed, in the form of a reply, Blessed are they that keep judgment I am of opinion, however, that the prophet had another design, namely, that there is no man who has ever endeavored to concentrate all his energies, both physical and mental, in the praising of God, but will find himself inadequate for so lofty a subject, the transcendent grandeur of which overpowers all our senses. Not that he exalts the power of God designedly to deter us from celebrating its praises, but rather as the means of stirring us up to do so to the utmost of our power. Is it any reason for ceasing our exertions, that with whatever alacrity we pursue our course, we yet come far short of perfection? But the thing which ought to inspire us with the greatest encouragement is, the knowledge that, though ability may fail us, the praises which from the heart we offer to God are pleasing to him; only let us beware of callousness; for it would certainly be very absurd for those who cannot attain to a tithe of perfection, to make that the occasion of their not reaching to the hundredth part of it.

Who can utter the mighty acts of the Lord? - Who can speak the great things of God? Who can find language which will suitably express what he has done, or which will "come up" in sublimity to his acts? In other words, human language must fall immeasurably short of adequately expressing the praises of Yahweh, or conveying the fullness of what he has done. Who has not felt this when he has endeavored to praise God in a proper manner? Compare the notes at Psalm 40:5.
Who can shew forth all his praise - Hebrew, "Cause to be heard." That is, Language cannot be found which would cause "it to be heard" in a suitable manner.

Who can utter the mighty acts of the Lord? - His acts are all acts of might; and particularly those in behalf of his followers.

Who can utter the mighty acts of the Lord?.... Or powers (i); to which answers the Greek word for the miracles of Christ, Matthew 11:20, and Kimchi here restrains them to the wonders wrought in Egypt, and at the Red sea: but they may as well be extended to the mighty acts of God, and the effects of his power, in the creation of all things out of nothing; in the sustaining and government of the world; in the redemption of his people by Christ; in the conversion of sinners, and in the final perseverance of the saints; in all which there are such displays of the power of God as cannot be uttered and declared by mortal tongues.
Who can show forth all his praise? all those things done by him, worthy of praise, they are so many and so great? see Psalm 40:5.
(i) "potentias", V. L. Michaelis; "virtutes", Cocceius.

His acts exceed our comprehension, as His praise our powers of expression (Romans 11:33). Their unutterable greatness is not to keep us back, but to urge us the more to try to praise Him as best we can (Psalm 40:5; Psalm 71:15).