Albert Barnes Commentary Psalms 89:10

"Thou hast broken Rahab in pieces, as one that is slain; Thou hast scattered thine enemies with the arm of thy strength." — Psalms 89:10 (ASV)

Thou hast broken Rahab in pieces — Margin, “Egypt.” See the notes at (Psalms 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 (Psalms 77:15). Compare (Deuteronomy 5:15); (Deuteronomy 7:8); (Deuteronomy 7:19), and others.