Isaiah 51:9
9Awake, awake, put on strength, arm of the LORD! Awake, as in the days of old, the generations of ancient times. Isn’t it you who cut Rahab in pieces, who pierced the monster?
Isn’t it you who cut Rahab in pieces, who pierced the monster? Wesley: Put on—put forth thy strength. Rahab—Egypt, from its pride or strength. The dragon—Pharaoh so called, Psa 74:13. The chapter-head still governs: a prayer of the Godly in affliction.
The cry is a prayer, not a feint; Rahab and the dragon are Egypt and Pharaoh at the Exodus, then gospel comfort. Common to both: awake; the arm; Rahab cut; the dragon pierced. Recall 51:1–2: look to Abraham; the God who called one can still put forth this arm. Compare 51:5: the coastlands wait for the same arm. Do not force Isa 53 onto the piercing here; Wesley does not go there.
Calvin: when God cheers us by his promises, we ought also to pray earnestly that he would perform what he has promised. He does not comfort us in order to render us slothful. Believers entreat the Lord to awake, not that they imagine him idle or asleep in heaven; they confess their own sluggishness. He is said to awake and put on strength when he exhibits testimonies of his power. The cause of the delay is that they had estranged themselves from God. Art thou not it that crushed the proud one? By Rahab he means proud and cruel Egypt; Ezekiel calls the king of Egypt a dragon. Art thou not it? The Lord is the same as he formerly was; he remains unchangeable.
Exodus first, then the same arm for the Church. Rahab as Egypt; the dragon as Pharaoh; the sea next. The arm the nations wait for in 51:5 is the same arm Zion now calls to wake, the arm that cut Rahab at the Exodus. Christ as Servant remains the light for the nations; this piercing is Egypt's dragon, not a forced Isa 53 atonement.
Key contrast Both hear Rahab as Egypt and the dragon as Pharaoh, the Exodus arm asked to act as of old. Wesley takes "put on" as put forth thy strength—the godly's prayer in affliction. Calvin grants the same cutting, then refuses a sleeping God: they confess their sluggishness; the delay is that they had estranged themselves; "Art thou not it?" because that arm, unlike a man's, does not decay.