Charles Spurgeon Commentary Jeremiah 9:3

"And they bend their tongue, [as it were] their bow, for falsehood; and they are grown strong in the land, but not for truth: for they proceed from evil to evil, and they know not me, saith Jehovah." — Jeremiah 9:3 (ASV)

And they bend their tongues like their bow for lies:

They made use of the tongue, as if it were a bow, to shoot out falsehood. It is a very graphic description of the men of Jeremiah's day. He dips his pen in his heart's blood as he writes about them.

But they are not valiant for the truth upon the earth;

Oh, no! No one stood up for the truth in those days; no man was willing to suffer for it, to argue for it, or even to own it.

For they proceed from evil to evil, and they know not me, says the LORD.

They grew worse and worse. It is the way of wicked men to ripen into greater sin. They proceeded from evil to evil; and Jeremiah had Jehovah's testimony for it that, though they knew a great many things, they did not know the LORD: They know not me, says the LORD.