Charles Ellicott Commentary Isaiah 51:9

"Awake, awake, put on strength, O arm of Jehovah; awake, as in the days of old, the generations of ancient times. Is it not thou that didst cut Rahab in pieces, that didst pierce the monster?" — Isaiah 51:9 (ASV)

Awake, awake. — Who is the speaker that so bursts into this grand apostrophe? (1) The redeemed and ideal Israel, or (2) the Servant of the Lord, or (3) the prophet, or (4) Jehovah, as in self-communing, as humans do, like that of Deborah in Judges 5:12. On the whole, the first seems the preferable view; but the loftiness of poetry, perhaps, transcends all such distinctions.

The appeal is, in any case, to the great deeds of God in the past, as the pledge and earnest of yet greater in the future. “Rahab,” as in Isaiah 30:7 and Psalm 89:10, is Egypt; and the “dragon,” like “leviathan” in Psalm 74:13, stands for Pharaoh. (Compare Ezekiel 29:3.) Cheyne quotes from Bunsen’s “Egypt,” volume 6, an invocation to the god Ra from the Egyptian Book of the Dead: “Hail, you who have cut in pieces the scorner and strangled Apophis (namely, the evil serpent),” as a striking parallel.