This very beautiful psalm is designed to illustrate the superiority of revealed truth above the light of nature in showing the character and perfections of God. In doing this, there is no attempt in the psalm, as there should be none on our part in explaining it, to undervalue or disparage the truths about God revealed by nature. All that could now be said in regard to the works of creation, as illustrating the divine perfections, is really admitted by the psalmist Psalm 19:1-6; and yet this is placed in strong contrast with the revelations disclosed in the "law of the Lord," that is, in his revealed word Psalm 19:7-11. The revelations of nature, and the higher revelation by inspiration, belong to the same system of religion, and are alike designed to illustrate the being, the perfections, and the government of God. The friend of religion should claim the one as well as the other; the defense of the Bible as a revelation from God should not lead us to disparage or undervalue the disclosures respecting God as made by nature. He who asserts that a revelation is necessary to mankind, and who maintains that the light of nature is not sufficient for the wants of man, should nevertheless concede all that can be known from the works of God about the Creator; should rejoice in all that truth; and should be willing that all should be learned that can be learned about God from his works. When all this is admitted, and all this learned, there will be still an ample field for the higher disclosures which revelation claims to make.
Nor did the psalmist apprehend that the revelations about God which are made in his works would be in conflict with those which are made in his word. He evidently felt, in looking at these works of creation, that he was learning truths which would in no manner contradict the higher truths communicated by revelation; that the investigation of the one might be pursued to any extent without showing that the other was needless, or bringing the truth of the other into peril.
This psalm consists properly of three parts:
I. The revelation of God in his works, Psalm 19:1-6.
II. The higher and more glorious revelation of himself in his law, Psalm 19:7-10.
III. The bearing of these truths on the present character and conduct of the author, and consequently their adaptedness to produce the same effect on others, Psalm 19:11-14.
(a) in warning men of the nature of sin, and thus keeping them from transgression, Psalm 19:11;
(b) in making them aware of the extent and depth of sin, and especially of secret faults, Psalm 19:12;
(c) in leading them to pray earnestly that they may be cleansed from secret faults, and be kept back or restrained from presumptuous sins, Psalm 19:12-13;
(d) in leading them to pray earnestly that their words and thoughts may be made acceptable to God, Psalm 19:14.
The psalm is said in the title to be "A Psalm of David;" and there is nothing in the psalm itself to create a doubt in regard to the correctness of this statement. It is impossible, however, to determine when, or in what circumstances, it was composed, for there are no internal marks which will fix it at any particular period of the life of the author. There is no allusion either to persecution or to triumph; to private, domestic, or public life - or to any of the known circumstances of the history of David. If a conjecture may be allowed, it would seem not improbable that it was composed in those calm periods of his history when he led a shepherd-life; when he had abundant time to contemplate the movements of the heavenly bodies by day and by night, and to meditate on them in contrast with the higher truths which God had made known in his law.
Rosenmuller conjectured at one time that the psalm was originally two, and that the two were afterward united into one. DeWette also looked favorably on this supposition. Rosenmuller, however, subsequently saw occasion to retract this, and to adopt the opinion that it was originally one composition. This is undoubtedly the correct idea, as appears not only from the fact that there is no evidence that these were two psalms, and from the general character and construction of the psalm, but from the fact that the conclusion Psalm 19:12-14 seems to be based on the contemplation of all the truth which God in any way makes known to the soul. On the supposition that the psalm is one, this is a proper termination of the whole composition. On the other supposition, no small part of the beauty of the psalm would be lost.
In respect to the meaning of the title, "To the chief Musician," see the introduction to Psalm 4:1-8.

The heavens and their host proclaim the majesty of God, Psalm 19:1-6; the excellence and perfection of the Divine law, Psalm 19:7-10; its usefulness, Psalm 19:11. The psalmist prays for pardon and preservation from sin, Psalm 19:12, Psalm 19:13; and thy his Words and thoughts may be holy, Psalm 19:14.
The title of this Psalm has nothing particular in it; but it is not very clear that it was written by David, to whom it is attributed; though some think that he composed it in the wilderness, while persecuted by Saul. For this opinion, however, there is no solid ground. There is no note in the Psalm itself to lead us to know when, where, or by whom it was written. It is a highly finished and beautiful ode.

INTRODUCTION TO PSALM 19
To the chief Musician, a Psalm of David. This psalm was penned by David, and inscribed to the chief musician, as others, to be used in public service, and was designed for Gospel times, as the subject of it shows; which is first, not an account of the light of nature, and then of the law of Moses, but of the Gospel of Christ; and especially as ministered in the times of the apostles, as a citation out of it in Romans 10:18, makes clear.

(Psalm 19:1-6) The glory of God's works.
(Psalm 19:7-10) His holiness and grace as shown in his word.
(Psalm 19:11-14) Prayer for the benefit of them.

Prayer to God, Whose Revelation of Himself Is Twofold
In the inscription of Ps 18 David is called עבד יהוה, and in Psalm 19:1-14 he gives himself this name. In both Psalm, in the former at the beginning, in the latter at the close, he calls upon Jahve by the name צוּרי, my rock. These and other points of contact (Symbolae p. 49) have concurred to lead the collector to append Psalm 19:1-14, which celebrates God's revelation of Himself in nature and in the Law, to Ps 18, which celebrates God's revelation of Himself in the history of David. The view, that in Psalm 19:1-14 we have before us two torsi blown together from some quarter or other, is founded upon a defective insight into the relationship, which accords with a definite plan, of the two halves Psalm 19:2, Psalm 19:8, as Hitzig has recently shown in opposition to that view. The poet begins with the praise of the glory of God the Creator, and rises from this to the praise of the mercy of God the Lawgiver; and thus through the praise, springing from wondering and loving adoration, he clears the way to the prayer for justification and sanctification. This prayer grows out of the praise of the mercy of the God who has revealed Himself in His word, without coming back to the first part, Psalm 19:2. For, as Lord Bacon says, the heavens indeed tell of the glory of God, but not of His will, according to which the poet prays to be pardoned and sanctified. Moreover, if we suppose the Psalm to be called forth by the aspect of the heavens by day, just as Psalm 8:1-9 was by the aspect of the heavens by night, then the unity of this praise of the two revelations of God becomes still more clear. It is morning, and the psalmist rejoices on the one hand at the dawning light of day, and on the other he prepares himself for the days' work lying before him, in the light of the Tפra. The second part, just like the first part, consists of fourteen lines, and each of them is naturally divided into a six and an eight line strophe. But in the second part, in the place of the short lines comes the caesural schema, which as it were bounds higher, draws deeper breaths and surges as the rise and fall of the waves, for the Tפra inspires the psalmist more than does the sun. And it is also a significant fact, that in the first part God is called אל according to his relationship of power to the world, and is only mentioned once; whereas in the second part, He is called by His covenant name יהוה, and mentioned seven times, and the last time by a threefold name, which brings the Psalm to a close with a full toned יהוה צורי וגאלי. What a depth of meaning there is in this distinction of the revelation of God, the Redeemer, from the revelation of God, the Creator!
The last strophe presents us with a sharply sketched soteriology in nuce. If we add Psalm 32:1-11, then we have the whole of the way of salvation in almost Pauline clearness and definiteness. Paul, moreover, quotes both Psalm; they were surely his favourites.