Jeremías 9:5

And they will deceive everyone his neighbour ,.... In conversation, with lying words; and in trade and commerce, by art and tricking:

and will not speak the truth ; with respect to facts they report, or goods they sell:

they have taught their tongue to speak lies ; and become so accustomed to lying that they cannot do otherwise; it is as it were natural to them:

and weary themselves to commit iniquity ; spared no pains to come at it, nor any in it, and go on even to weariness; are more laborious and indefatigable in committing sin than good men are in doing good; which shows great folly and stupidity. The Targum is,

"they are become foolish, they have erred.'