Day unto day uttereth speech. Philosophers, who have more penetration into those matters than others, understand how the stars are arranged in such beautiful order, that notwithstanding their immense number there is no confusion; but to the ignorant and unlettered, the continual succession of days is a more undoubted proof of the providence of God. David, therefore, having spoken of the heavens, does not here descend from them to other parts of the world; but, from an effect more sensible and nearer our apprehension, he confirms what he has just now said, namely, that the glory of God not only shines, but also resounds in the heavens. The words may be variously expounded, but the different expositions which have been given of them make little difference as to the sense. Some explain them thus, that no day passes in which God does not show some signal evidence of his power. Others are of opinion that they denote the augmentations of instruction and knowledge, - that every succeeding day contributes something new in proof of the existence and perfections of God. Others view them as meaning that the days and nights talk together, and reason concerning the glory of their Creator', but this is a somewhat forced interpretation. David, I have no doubt, here teaches, from the established alternations of days and nights, that the course and revolutions of the sun, and moon, and stars, are regulated by the marvellous wisdom of God. Whether we translate the words Day after day, or one day to another day, is of little consequence; for all that David means is the beautiful arrangement of time which the succession of days and nights effects. If, indeed, we were as attentive as we ought to be, even one day would suffice to bear testimony to us of the glory of God, and even one night would be sufficient to perform to us the same office. But when we see the sun and the moon performing their daily revolutions, -- the sun by day appearing over our heads, and the moon succeeding in its turns -- the sun ascending by degrees, while at the same time he approaches nearer us, -- and afterwards bending his course so as to depart from us by little and little; -- and when we see that by this means the length of the days and nights is regulated, and that the variation of their length is arranged according to a law so uniform, as invariably to recur at the same points of time in every successive year, we have in this a much brighter testimony to the glory of God. David, therefore, with the highest reason, declares, that although God should not speak a single word to men, yet the orderly and useful succession of days and nights eloquently proclaims the glory of God, and that there is now left to men no pretext for ignorance; for since the days and nights perform towards us so well and so carefully the office of teachers, we may acquire, if we are duly attentive, a sufficient amount of knowledge under their tuition.

Day unto day - One day to another; or, each successive day. The day that is passing away proclaims the lesson which it had to convey from the movements of the heavens, about God; and thus the knowledge of God is accumulating as the time moves on. Each day has its own lesson in regard to the wisdom, the power, and the goodness of God, and that lesson is conveyed from one day to another. There is a perpetual testimony thus given to the wisdom and power of the Great Creator.
Uttereth speech - The word here rendered uttereth means properly to pour forth; to pour forth copiously as a fountain. Compare Proverbs 18:4; Proverbs 1:23; Proverbs 15:2, Proverbs 15:28. Hence, the word means to utter; to declare. The word "speech" means properly "a word;" and then, "a lesson;" or "that which speech conveys." The idea is, that the successive days thus impart instruction, or convey lessons about God. The day does this by the returning light, and by the steady and sublime movement of the sun in the heavens, and by all the disclosures which are made by the light of the sun in his journeyings.
And night unto night showeth knowledge - Knowledge respecting God. Each successive night does this. It is done by the stars in their courses; in their order; their numbers; their ranks; their changes of position; their rising and their setting. There are as many lessons conveyed to man about the greatness and majesty of God by the silent movements of each night as there are by the light of the successive days - just as there may be as many lessons conveyed to the soul about God in the dark night of affliction and adversity, as there are when the sun of prosperity shines upon us.

Day unto day uttereth speech - Each day is represented as teaching another relative to some new excellence discovered in these manifold works of God. The nights also, by the same figure, are represented as giving information to each other of the increase of knowledge already gained.
"The labors of these our instructers know no intermission; but they continue incessantly to lecture us in the science of Divine wisdom. There is one glory of the sun, which shines forth by day; and there are other glories of the moon and of the stars, which become visible by night. And because day and night interchangeably divide the world between them, they are therefore represented as transmitting, in succession, each to other, the task enjoined them, like the two parts of a choir, chanting forth alternately the praises ot God." - Bisbop Horne.

(b) Day unto day uttereth speech, and night unto night sheweth knowledge.
(b) The continual success of the day and night is sufficient to declare God's power and goodness.

Day untoday uttereth speech,.... This, with the following clause,
and night untonight showeth knowledge, some understand of the constant and continued succession of day and night; which declares the glory of God, and shows him to be possessed of infinite knowledge and wisdom; and which brings a new accession of knowledge to men; others, of the continual declaration of the glory of God, and of the knowledge of him made by the heavens and the firmament, the ordinances of which always continue; the sun for a light by day, and the moon and stars for a light by night; and so night and day constantly and successively proclaim the glory and wisdom of God: but rather this is to be understood of the constancy of the Gospel ministry, and the continuance of the evangelic revelation. The apostles of Christ persevered in their work, and laboured in the word and doctrine night and day: they were in it at all seasons; yea, were instant in season and out of season; and though they are dead, the Gospel continues, and will do as long as day and night remain: and these, like overflowing fountains, sent forth in great abundance, as the word (x) rendered "uttereth" signifies, the streams of divine light and knowledge; they were full of matter, and their tongues were as the pen of a ready writer; they diffused the savour of the knowledge of Christ, in great plenty, in every place where they came. These words express the continuance of the Gospel revelation, as the next do the extent of it.
(x) "eructat", Musculus, Munster, Vatablus, Junius & Tremellius, Piscator; so Ainsworth; "scaturit", Muis; "scaturiendo effundit", Cocceius; "copiose ac constanter instar foecundae cujusdam scaturiginis protrudit, emittit", Gejerus; so Michaelis.

uttereth--pours forth as a stream; a perpetual testimony.

Day - Every day and night repeats these demonstrations of God's glory. Uttereth - Or, poureth forth, constantly and abundantly, as a fountain doth water; So this Hebrew word signifies. Knowledge - Gives us a clear knowledge or discovery of God their author.