Albert Barnes Commentary Jonah 2:9

"But I will sacrifice unto thee with the voice of thanksgiving; I will pay that which I have vowed. Salvation is of Jehovah." — Jonah 2:9 (ASV)

But (And) with the voice of thanksgiving I will (I would gladly) sacrifice to You; what I have vowed, I would pay - He does not say, "I will," because it did not depend on him. Without a further miracle of God, he could do nothing. But he says that he would never again forsake God.

The law appointed sacrifices of thanksgiving (Leviticus 7:12–15); these he would offer, not in act only, but with words of praise. He would pay what he had vowed, and chiefly himself, his life which God had given back to him, the obedience of his remaining life, in all things. For , he that keeps the law brings offerings enough; he that takes heed to the commandments offers a peace-offering. Jonah neglects neither the outward nor the inward part, neither the body nor the soul of the commandment.

Salvation is of the Lord (literally to the Lord) - It is wholly His; all belongs to Him, so that none can share in bestowing it; none can have any hope, except from Him. He uses an intensive form, as though he would say, strong “mighty salvation”.

God seems often to wait for the full resignation of the soul, all its powers and will to Him. Then He can show mercy healthfully, when the soul is wholly surrendered to Him. So, on this full confession, Jonah is restored. The prophet’s prayer ends almost in promising the same as the mariners: they “made vows;” Jonah says, I will pay that I have vowed. Devoted service in the creature is one and the same, although diverse in degree. And so, that Israel might not despise the pagan, he tacitly likens the act of the new pagan converts and that of the prophet.