Charles Spurgeon Commentary Jeremiah 9:13-14

"And Jehovah saith, Because they have forsaken my law which I set before them, and have not obeyed my voice, neither walked therein, but have walked after the stubbornness of their own heart, and after the Baalim, which their fathers taught them;" — Jeremiah 9:13-14 (ASV)

And the LORD saith, Because they have forsaken my law which I set before them, and have not obeyed my voice, neither walked therein; but have walked after the imagination of their own heart, and after Baalim,

'After many Baals' is the meaning; many are the gods that men make for themselves when they turn away from Jehovah.