The "fierceness of his wrath" represents God's anger and punishment. Throwing the punishment on him represents punishing him severely. Alternate translation: "God will be angry and throw down his punishment on him" or "God will be angry and punish him severely" (See: [[rc://en/ta/man/jit/figs-metaphor]])
"God will cause it to rain down on him." Here "rain it down on him" represents causing much punishment to happen to the man. Alternate translation: "God will punish him severely" (See: [[rc://en/ta/man/jit/figs-metaphor]])