God be merciful unto us, and bless us; and cause his face to shine upon us. This is a fit refrain to the benediction of the High Priest in the name of the Lord, as recorded in Nu 6:24-25.

That thy way may be known upon earth. As showers which first fall upon the hills afterwards run down in streams into the valleys, so the blessing of the Most High comes upon the world through the church. We are blessed for the sake of others as well as ourselves.

Let the people praise thee, O God. Cause them to own thy goodness and thank thee with all their hearts; let nations do this, and do it continually, being instructed in thy gracious way. Let all the people praise thee.

O let the nations be glad and sing for joy, or, they shall joy and triumph. When men know God's way and see his salvation, it brings to their hearts much happiness. Nothing creates gladness so speedily, surely, and abidingly as the salvation of God.

These words are no vain repetition, but are a chorus worthy to be sung again and again. The great theme of the psalm is the participation of the Gentiles in the worship of Jehovah; the psalmist is full of it, he hardly knows how to contain or express his joy.

Then shall the earth yield her increase. Sin first laid a curse on the soil, and grace alone can remove it. Under tyrannical governments lands become unproductive; even the land which flowed with milk and honey is almost a wilderness under Turkish rule; but, when the principles of true religion…

God shall bless us. The prayer of the first verse is the song of the last. We have the same phrase twice, and truly the Lord's blessing is manifold; he blesses and blesses and blesses again. How many are his beatitudes! How choice his benedictions! They are the peculiar heritage of his chosen.

God be merciful unto us, and bless us, etc. God forgives, then he gives; till he be merciful to pardon our sins through Christ, he cannot bless or look kindly on us sinners. All our enjoyments are but blessings in bullion, till gospel grace and pardoning mercy stamp and make them current.

That thy way may be known, etc. The psalmist here supposes that there are certain rules or principles, in accordance with which God bestows blessings on mankind; and he prays that those rules and principles may be everywhere made known upon the earth. Albert Barnes. That thy way may be known, etc.

Let the people praise thee. Mark the sweet order of the blessed Spirit: first, mercy; than, knowledge; last of all, praising of God. We cannot see his countenance except he be merciful to us; and we cannot praise him except his way be known upon earth.

For thou shalt judge the people righteously, etc. The Psalmist may here seem to contradict himself; for if mercy make men rejoice, then judgment occasions men to tremble.

Let the people praise thee, O God; let all the people praise thee! What then? Then shall the earth yield her increase; and God, even our own God, shall bless us. Our unthankfulness is the cause of the earth's unfruitfulness.

Then shall the earth yield her increase. An increase of wealth is but the natural result of increased piety and intelligence. There are certain qualities essential to temporal prosperity. These are industry, economy, moderation; and such are the qualities begotten of godliness. . . .

Note, how joy in God, and fear of God, are combined. By joy the sadness and anxiety of diffidence are excluded, but by fear contempt and false security are banished. So Psalm 2, "Serve the Lord with fear, and rejoice with trembling." Wolfgang Musculus.