Thou hast broken Rahab - Thou hast destroyed the power of Egypt, having overthrown the king and its people when they endeavored to prevent thy people from regaining their liberty.
As one that is slain - The whole clause in the original is, רהב כחלל דכאת אתה attah dikkitha kechalal Rahab, "Thou, like a hero, hast broken down Egypt." Dr. Kennicott has largely proved that חלל chalal, which we render wounded, slain, etc., means a soldier, warrior, hero; and it is certain that this sense agrees better with it than the other in a great number of places. Mr. Berlin translates, Tu contrivisti ut cadaver Aegyptum; "Thou hast bruised down Egypt like a dead carcass." The whole strength of Egypt could avail nothing against thee. Thou didst trample them down as easily as if they had all been dead carcasses.
Thou hast broken Rahab in pieces - Margin, “Egypt.” See the notes at Psalm 87:4. The reference is to the exodus of the Hebrew people, when he destroyed the power of Egypt.
As one that is slain - Slain on the field of battle; as a man pierced through with a sword or spear.
Thou hast scattered thine enemies - At the time referred to, in Egypt; and at other times, when the enemies of God and of his people had been discomfited.
With thy strong arm - Margin, as in Hebrew, the arm of thy strength. That is, by his power - the arm being the symbol of power. See the notes at Psalm 77:15. Compare Deuteronomy 5:15; Deuteronomy 7:8, Deuteronomy 7:19, et al.