Seeing his days are determined - The general term of human life is fixed by God himself; in vain are all attempts to prolong it beyond this term. Several attempts have been made in all nations to find an elixir that would expel all the seeds of disease, and keep men in continual health; but all these attempts have failed. Basil, Valentine, Norton, Dastin, Ripley, Sandivogius, Artephius, Geber, Van Helmont, Paracelsus, Philalethes, and several others, both in Europe and Asia, have written copiously on the subject, and have endeavored to prove that a tincture might be produced, by which all imperfect metals may be transmuted into perfect; and an elixir by which the human body may be kept in a state of endless repair and health. And these profess to teach the method by which this tincture and this elixir may be made! Yet all these are dead; and dead, for aught we know, comparatively young! Artephius is, indeed, said to have lived ninety years, which is probable; but some of his foolish disciples, to give credit to their thriftless craft, added another cipher, and made his age nine hundred! Man may endeavor to pass the bound; and God may, here and there, produce a Thomas Parr, who died in 1635, aged one hundred and fifty-two; and a Henry Jenkins, who died in 1670, aged one hundred and sixty-nine; but these are rare instances, and do not affect the general term. Nor can death be avoided. Dust thou art, and unto dust thou shalt return, is the law, and that will ever render nugatory all such pretended tinctures and elixirs. But, although man cannot pass his appointed bounds, yet he may so live as never to reach them; for folly and wickedness abridge the term of human life; and therefore the psalmist says, Bloody and deceitful men shall not live out Half their days, Psalm 55:23, for by indolence, intemperance, and disorderly passions, the life of man is shortened in cases innumerable. We are not to understand the bounds as applying to individuals, but to the race in general. Perhaps there is no case in which God has determined absolutely that man's age shall be so long, and shall neither be more nor less. The contrary supposition involves innumerable absurdities.
Seeing his days - are “determined” Since man is so frail, and so short-lived, let him alone, that he may pass his little time with some degree of comfort and then die; see the notes at Job 7:19-21. The word “determined” here means “fixed, settled.” God has fixed the number of his days, so that they cannot be exceeded; compare the notes at Isaiah 10:23, and notes at Psalm 90:10.
The number of his months are with thee - Thou hast the ordering of them, or they are determined by thee.
Thou hast appointed his bounds - Thou hast fixed a limit, or hast determined the time which he is to live, and he cannot go beyond it. There is no elixir of life that can prolong our days beyond that period. Soon we shall come to that outer limit of life, and then we must die. When that is we know not, and it is not desirable to know. It is better that it should be concealed. If we knew that it was near, it would fill us with gloom, and deter us from the efforts and the plans of life altogether. If it were remote, we should be careless and secure, and should think there was time enough yet to prepare to die. As it is, we know that the period is not very far distant; we know not but that it may be very near at hand, and we would be always ready.