For thou art great, and thou alone, O God! doest wondrous things. In this verse there is again repeated the cause which will bring all nations to worship before the Lord, namely, the discovery made of his glory by the greatness of his works. The contemplation of God's glory in his works is the true way of acquiring genuine godliness. The pride of the flesh would always lead it to wing its way into heaven; but, as our understandings fail us in such an extended investigation, our most profitable course is, according to the small measure of our feeble capacity, to seek God in his works, which bear witness of him. Let us therefore learn to awaken our understandings to contemplate the divine works, and let us leave the presumptuous to wander in their own intricate mazes, which, in the end, will invariably land them in an abyss from which they will be unable to extricate themselves. To incline our hearts to exercise this modesty, David magnificently extols the works of God, calling them wondrous things, although to the blind, and those who have no taste for them, they are destitute of attraction. In the meantime, we ought carefully to attend to this truth, That the glory of Godhead belongs exclusively to the one true God; for in no other being is it possible to find the wisdom, or the power, or the righteousness, or any of the numerous marks of divinity which shine forth in his wonderful works. Whence it follows, that the Papists are chargeable with rendering, as much as in them lies, his title to true Godhead nugatory, when despoiling him of his attributes they leave him almost nothing but the bare name.

For thou art great, and doest wondrous things - Things suited to excite wonder or admiration; things which lie beyond the power of any creature, and which could be performed by no one but a being of almighty power. A God who could do these things could also do that which the psalmist asked of him, for what God actually does proves that there is nothing within the limits of possibility which he cannot perform. The greatness and the power of God are reasons why we should appeal to him in our weakness, and in our times of trouble.
Thou art God alone - Thou only canst do what a God can do, or what belongs to God. In those things, therefore, which require the interposition of divine power our appeal must be to thee alone. So in the matter of salvation.

For thou art great - Almighty, infinite, eternal.
And doest wondrous things - ועשה נפלאות veoseh niphlaoth; thou art the Worker of miracres. This thou hast done in numerous instances, and thereby showed thy infinite power and wisdom.
This appears to be a prophecy of the calling of the Gentiles to the faith of Christ, and the evidence to be given to his Divine mission by the miracles which he should work.
Thou art God alone - Συ ει ὁ Θεος μονος ὁ μεγας - Sept. Thou art the only, The Great God. In this the Ethiopic and Arabic agree.

For thou art great,.... In his nature, and the perfections of it; in his power, wisdom, truth, faithfulness, love, grace, and mercy; and in all his persons; the Father is great, greater than all; the Son is the great God, and our Saviour; and the Spirit, which is in his people, is greater than he that is in the world:
and doest wondrous things; in nature and providence; such as the forming of all things out of nothing; upholding all things by the word of his power; the formation of man, soul and body, and the union of both; and the constant government of the world; and more especially in grace, as the provision in the covenant in eternity, the mission of Christ in time, the conversion of a sinner, and bringing him to eternal glory:
thou art God alone; to the exclusion of all such who are not gods by nature; but not to the exclusion of the Son and Spirit, who are, with the Father, the one God, 1-John 5:7.