Clearly, there is great similarity between Psalm 19 and Psalm 119, but there is also dissimilarity. The similarity, of course, is that the law of God is the focus for extolling all of the Word of God. The dissimilarity is that Psalm 19 is both more concise (after all, Psalm 119 is 176 verses) and more specific or more to the point. The author of this psalm is David. He uses law, statutes, precepts, commandments, fear, and ordinances as part of the means by which he intends to teach us something vital.
One might wonder why fear is included. It is because fear represents the specific attitude required to make the best use of God's law. Solomon writes in Proverbs 9:10, "The fear [a deep and abiding respect tinged with terror] of the LORD is the beginning of wisdom." In addition, remember that wisdom is right application of knowledge and understanding. If fear is not present, we will not even start to build towards faith, hope, and love. Godly fear gets us jump-started, gets us going to do what is right.
Psalm 19 is divided into three sections: The first section—beginning with "The heavens declare the glory of God" and concluding in verse 6—concerns the revelation of the Creator God in His creation. The second part, beginning with verse 7 and extending through verse 11, is the revelation of the Covenant God in His Word, most specifically in His law. The third part comprises the last few verses, and it contains the response of the man of faith to the first two sections.
In "the heavens declare the glory of God," the word "God" is not Elohim but the singular El. In verse 7, LORD is Yahweh. Thus, the same Being is identified as El and Yahweh. Through this psalm, David is saying that, though the creation reveals the majesty and the power—the implication of the name "El"—of the One who created, the law of God reveals in a much clearer, more comprehensive way the specifics of the nature, character, and purpose of that Being—as suggested by the name "Yahweh." God's law is, therefore, of far more practical help to the created, us.
Thus, he makes a comparison. He says, "Here is the creation. It is great and good. However, it does not even begin to teach you as the law of God does." The specifics that we need about how to live are in the law of God. Both are needed, but the revelation of the law takes one far beyond the nature of the creation.
John W. Ritenbaugh
The Covenants, Grace, and Law (Part 14)