Jonah 2:8

They that observe lying vanities forsake their own mercy.
] They that worship idols, who are nothing, mere vanity and lies, and deceive those that serve them, these forsake the God of their lives, and of their mercies; and so do all such who serve divers lusts and pleasures, and pursue the vanities of this life; and also those who follow the dictates of carnal sense and reason, to the neglect of the will of God, and obedience to his commands; which was Jonah's case, and is, I think, chiefly intended. The Targum, Syriac version, and so Jarchi, and most interpreters, understand it of worshippers of idols in general; and Kimchi of the mariners of the ship Jonah had been in; who promised to relinquish their idols, but did not; and vowed to serve the Lord, and sacrifice to him, but did not perform what they promised. But I rather think Jonah reflects upon himself in particular, as well as leaves this as a general instruction to others; that should they do as he had done, give way to an evil heart of unbelief, and attend to the suggestions of a vain mind, and consult with flesh and blood, and be directed thereby, to the disregard of God and his will; they will find, as he had done to his cost, that they forsake that God that has been gracious and merciful to them, and who is all goodness and mercy, ( Psalms 144:3 ) ; which to do is very ungrateful to him, and injurious to themselves; and now he being sensible of his folly, and influenced by the grace and goodness of God to him, resolves to do as follows: