C. F. Keil and Franz Delitzsch on Jonah 1:15-16

Jon 1:15-16

After they had prayed thus, they cast Jonah into the sea, and “the sea stood still (ceased) from its raging.” The sudden cessation of the storm showed that the bad weather had come entirely on Jonah’s account, and that the sailors had not shed innocent blood by casting him into the sea. In this sudden change in the weather, the arm of the holy God was so suddenly manifested, that the sailors “feared Jehovah with great fear, and offered sacrifice to Jehovah” - not after they landed, but immediately, on board the ship - “and vowed vows,” i.e., vowed that they would offer Him still further sacrifices on their safe arrival at their destination.