Then shall the dust return to the earth as it was: and the spirit shall return unto God who gave it.
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Augustine of Hippo
AD 430
Near the end of the book called Ecclesiastes there is a passage about the dissolution of man, brought about by that death through which the soul is separated from the body, where the Scripture says, “And let the dust return into its earth, as it was, and the spirit return to God who gave it.” This authoritative statement is unquestionably true and leads no one into error. But if anyone wished to interpret it so as to try to defend the view that there was a posterity of souls and that all the subsequent ones come from that one which God gave to the first man, this passage seems to support him. [This is so] because flesh is there spoken of as dust—obviously, dust and spirit mean nothing else in this passage than flesh and soul—and in that way it declares that the soul returns to God, as if it might be a sort of branch, cut from that soul which God gave to the first man, just as the flesh is returned to the earth, since it is an offshoot of that flesh that in the first man was fashioned o...
We ask that the will of God may be done both in heaven and in earth, each of which things pertains to the fulfillment of our safety and salvation. For since we possess the body from the earth and the spirit from heaven, we ourselves are earth and heaven; and in both—that is, both in body and spirit—we pray that God’s will may be done. The Lord’s Prayer
It. Man is composed of two distinct parts; the destination of which we ought never to forget. Thus the objection of infidels (chap. iii. 19.) is refuted. Plato and some of the ancients had the same idea of the soul's spiritual nature; though some took it to be an aerial body. (Calmet)
“Before the dust returns to the earth as it was, and the spirit returns to God, who gave it.” What could be said more clearly than his having declared the stuff of the flesh, which he has called dust because it originated from the seed of man and seems to be sown by his doing, will return to the earth once more just as it was taken from the earth? Whereas he has indicated that the spirit, which is not begotten from the mingling of the sexes but is bestowed particularly by God alone, will return to its Creator? This is clearly expressed, too, by that inbreathing of God by which Adam was first ensouled. .