John Calvin Commentary Psalms 104:14

"He causeth the grass to grow for the cattle, And herb for the service of man; That he may bring forth food out of the earth," — Psalms 104:14 (ASV)

Making grass to grow for cattle. The Psalmist now comes to humankind, for whom God graciously takes special care as His children. After speaking of the animal creation, he declares that grain is produced, and bread made from it, for the nourishment of humankind. He also mentions wine and oil, two things that not only supply the needs of humankind but also contribute to their cheerful enjoyment of life.

Some understand the Hebrew word לעבדת, laäbodath, which I have translated for the service, to signify the labor that people perform in agriculture. For while grass grows on the mountains by itself and without human labor, grain and plants, which are sown, can, as is well known, only be produced by human labor and sweat.

According to them, the meaning is that God blesses human toil in the cultivation of the fields. However, since this is too forced an interpretation, it is better to understand the word service in its ordinary sense. Regarding the word bread, I do not object to the view of those who understand it in a restricted sense, although it probably includes all kinds of food; I simply dislike the opinion of those who exclude bread.

The reason they offer for this view holds no weight—namely, that the following verse adds another use of bread when it says, that it strengthens the heart of man; for the same idea is expressed there in different words. The prophet, in stating that God causes the earth to bring forth herbs for human support, intends to say that the earth supplies them not only with food from grain but also with other herbs and fruits, for our means of sustenance is not limited exclusively to one kind of food.