Charles Ellicott 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)

Your heaven ... shall be brass, and the earth ... iron. —Not only regarding the drought, but also God’s refusal to remove it. See Jeremiah 14:15 for a most sorrowful intercession for Israel under this misery, answered with the command, Pray not for this people for their good (Jeremiah 14:11). Only grief is permitted (Deuteronomy 28:17). Relief is not given (Deuteronomy 15:1).