Adam Clarke on Ecclesiastes 12:7

Then shall the dust return to the earth as it was: and the spirit shall return unto God -

5. Putrefaction and solution take place; the whole mass becomes decomposed, and in process of time is reduced to dust, from which it was originally made; while the spirit, הרוח haruach, that spirit, which God at first breathed into the nostrils of man, when he in consequence became a Living Soul, an intelligent, rational, discoursing animal, returns to God who gave it. Here the wise man makes a most evident distinction between the body and the soul: they are not the same; they are not both matter. The body, which is matter, returns to dust, its original; but the spirit, which is immaterial, returns to God. It is impossible that two natures can be more distinct, or more emphatically distinguished. The author of this book was not a materialist.

Thus ends this affecting, yet elegant and finished, picture of Old Age and Death. See a description of old age similar, but much inferior, to this, in the Agamemnon of Aeschylus, 5:76-82.

It has been often remarked that the circulation of the blood, which has been deemed a modern discovery by our countryman Dr. Harvey, in 1616, was known to Solomon, or whoever was the author of this book: the fountains, cisterns, pitcher, and wheel, giving sufficient countenance to the conclusion.