John Calvin 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. Here the Prophet instructs us that 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 make us slothful, but so that we may be inflamed with a stronger desire to pray and may continually exercise our faith.

The Prophet speaks according to our feelings, for we think that God is asleep as long as He does not come to the relief of our needs; and the Lord indulges us so far as to permit us to speak and pray according to the feeling of our weakness.

Believers therefore entreat the Lord to “awake.” This is not because they imagine Him to be idle or asleep in heaven. On the contrary, they confess their own sluggishness and ignorance, in not being able to form any conception of God as long as they are not aware of receiving His assistance.

Yet, though the flesh imagines that He is asleep or that He disregards our calamities, faith rises higher and lays hold of His eternal power.

Put on strength, O arm of Jehovah. He is said to “awake” and “put on strength” when He exhibits testimonies of His power, because otherwise we think that He is idle or asleep. Meanwhile, the Prophet, by addressing the arm of God which was concealed, holds it out to the view of believers as actually present, so that they may be convinced that the only reason they are so bitterly and painfully afflicted by their enemies is because God has withdrawn His aid. The cause of the delay has already been shown: they had estranged themselves from God.

In ancient days. By the term “ancient days” he shows that we ought to remember all that the Lord did long ago for the salvation of His people. Though He appears to pause and to take no more care about us, still He is the same God who formerly governed His Church; and therefore He can never forsake or abandon those whom He takes under His protection.

In ages long ago past. This repetition tells us still more clearly that we ought to consider not only those things which have happened lately, but also those which happened long ago; for we ought to stretch our minds even to the most remote ages, so that they may rise above temptations, which otherwise might easily overwhelm us.

Art thou not it that crushed the proud one? The numerous testimonies of grace which God had displayed in various ages are here collected by the Prophet, so that if a few are not enough, the vast number of them may altogether confirm the faith of the Church.

But since it would be too tedious to draw up an entire catalogue, he brings forward that singular and most remarkable of all such events: namely, that the people were once delivered from Egypt in a miraculous manner.

For I have no doubt that by Rahab he means proud and cruel Egypt. As it is also said: “I will mention Rahab and Babylon among my friends” (Psalms 87:4).

Similarly, Ezekiel calls the king of Egypt “a Dragon”: “Behold, I am against thee, O Pharaoh, king of Egypt, the great dragon, who dwellest in the midst of thy rivers” (Ezekiel 29:3).

It is sufficiently evident, and universally admitted, that the Prophet here recalls the miraculous deliverance of the people from Egypt. “If at that time the pride of Egypt was tamed and subdued, if the dragon was put to flight, why should we not hope for the same thing?”

By putting the question, whether it is the same arm, he argues from the nature of God. For could such a thing be affirmed respecting the “arm” of man, whose strength, though great, diminishes and fails with time?

Milo, who had been very strong, when he became old and looked at his arms, groaned because the strength he possessed at an earlier period had then left him. But it is not so with God, whose strength no lapse of time can diminish.

These words ought to be read ἐμφατικῶς (emphatically): “Art thou not it?” For he shows that the Lord is the same as He formerly was, because He remains unchangeable.