מֵ֭פֵר מַחְשְׁב֣וֹת עֲרוּמִ֑ים וְֽלֹא־תַעֲשֶׂ֥ינָה יְ֝דֵיהֶ֗ם תּוּשִׁיָּֽה׃
He frustrateth the devices of the crafty, So that their hands can perform nothing substantial.
Rashi on Job
so that their hands do not carry out their plans The counsel that they planned to perform.
Malbim on Job
As an example of this, Malbim cites the way the Lord frustrated the scheme to kill David presented by Ahitophel to Absalom (vide 2Samuel 17:14).