With his glorious arm. — Literally, with the arm of His glory, or majesty. This, the arm of the Unseen Guide, is thought of as accompanying the leader of Israel, ready to grasp his hand and support him in time of need.
Dividing the water. — The words may include the passage of the Jordan, but refer primarily to that of the Red Sea. (Comp. Psalms 77:16; Psalms 106:9.)