John Calvin Commentary Deuteronomy 28:23

"And thy heaven that is over thy head shall be brass, and the earth that is under thee shall be iron." — Deuteronomy 28:23 (ASV)

And thy heaven that is over thy head. He enumerates other causes of barrenness, and especially drought. Often God, through the Prophets, desiring to give a token of His favor toward the people, promises them the rain of autumn and of spring: the one immediately following the sowing, the other giving growth to the fruits before they begin to ripen; while in many passages He also threatens that it should be withheld.

To this refers what He now says, that the heavens shall be of brass, and the earth of iron, because moisture shall neither descend from heaven to fertilize the earth, while the earth, bound up and hardened, shall have no juice or dampness for production. From this we gather that not even a drop of rain falls to the earth except distilled by God, and that whenever it rains, the earth is irrigated as if by His hand.

It must, however, be observed, as we have seen before, that the land of Canaan was not like Egypt, which was watered by the care and industry of man, but fertilized by the bounty of heaven. Thus God, by the Prophet, marks the degrees which are worthy of observation, namely, that when He is reconciled to His people, He will hear the heavens, and they shall hear the earth; and the earth shall hear the corn, and the wine, and the oil; so that, finally, all these things shall hear starving men (Hosea 2:21–22).²⁴⁰

It is not superfluous that He should expressly speak of the heaven over our head, and the earth that is under our feet, for He thus indicates that His weapons are prepared both above and below to execute His vengeance, so as to assail the people on all sides. Another Prophet confirms this, although only in a brief allusion:

Therefore the heaven over you is stayed from dew, and the earth is stayed from her fruit; and I called for a drought, etc. (Haggai 1:10–11).

Another mode of expression is then used to make the same thing more sure, namely, that the rain should be turned into powder and dust; still, this clause may be explained in two ways: either that the rain will fertilize the ground no more than if it were ashes, or that, instead of rain, dust should fall, as though God would dry up the rich soil by scattering ashes on it.

²⁴⁰ See C. . in loco. Calvin Society’s edit., . Calvin Society’s edit., vol. 1, p. 118..