Albert Barnes Commentary Jonah 1:12

"And he said unto them, Take me up, and cast me forth into the sea; so shall the sea be calm unto you: for I know that for my sake this great tempest is upon you." — Jonah 1:12 (ASV)

Take me up, and cast me into the sea - Neither could Jonah have said this, nor could the sailors have obeyed it, without the command of God. Jonah might have wished to perish alone, as he alone had offended; but, without the command of God, the Giver of life, neither Jonah nor the sailors could dispose of the life of Jonah.

But God willed that Jonah should be cast into the sea—where he had gone for refuge—so that by means of which he had sinned, by the same also he might be punished as a man; and, as a prophet, so that he might, in his three days’ burial, prefigure Him who, after His Resurrection, should convert not Nineveh but the world, the cry of whose wickedness went up to God.

For I know that for my sake - “By saying, “I know,” he indicates that he had a revelation; by saying, “this great storm,” he indicates the necessity that lay upon those who cast him into the sea.”