Thou visitest the earth - God seems to come down that he may attend to the needs of the earth; survey the condition of things; arrange for the welfare of the world which he has made; and supply the needs of those whom he has created to dwell upon it. See the notes at Psalms 8:4.
And waterest it - Margin, After thou hadst made it to desire rain. This difference between the translations in the text and in the margin can be accounted for by the various meanings of the original word. The Hebrew term - שׁוק shûq - means properly:
(a) to run;
(b) to run after anything, to desire, to look for;
(c) to run over, to overflow; and then,
(d) to cause to overflow.
The meaning here evidently is, he drenched the earth, or caused the water to run abundantly. The reference is to a copious rain after a drought.
Thou greatly enrichest it - That is, Thou givest to it abundance; thou pourest water upon it in such quantities, and in such a manner, as to make it rich in its productions.
With the river of God - A river so abundant and full that it seems to come from God; it is such as we should expect to flow from a Being infinite in resources and in benevolence. Anything great is in the Scriptures often described as belonging to God, or his name is added to it to denote its greatness. Thus, hills of God mean lofty hills; cedars of God, lofty cedars, etc.
Which is full of water - The waters are so abundant that it seems as if they must come from God.
Thou preparest them corn - Grain. Thou givest to those who cultivate the earth an abundant harvest.
When thou hast so provided for it - Or rather, When thou hast thus prepared the earth, to wit, by sending down abundant rains upon it. God prepares the earth to bear an abundant harvest, and then he gives that harvest. The preparation of the earth for the harvest, and then the givinq of the harvest, are alike from him. The harvest could not be without the previous rain, and neither the rain nor the harvest could be without God. He does not create a harvest by miracle, but follows the order which he has himself ordained, and has respect to his own laws.