Isaiah 28:21

A second reason for the Jerusalemites’ terror (cf. Isaiah 28:18-19) would be divine hostility. The Lord would rise up against His people to defeat them, as He formerly rose up to defeat the Philistines at Mount Perazim (lit. breaking forth) "like the break-through of waters" (2 Samuel 5:20; 1 Chronicles 14:11). He had also defeated the Canaanites in the valley of Gibeon with hailstones (Joshua 10:11). Defeating the Israelites was strange work for the Lord because He customarily defended them. Judgment is His "strange work," especially judgment of His own people, a work foreign to what He usually does, namely: bless.