Psalms 64:3

Who whet their tongue like a sword, and bend their bows to shoot their arrows, even bitter words:

The verse pictures the wicked turning speech itself into a weapon, whetting the tongue as a man whets a sword and bending the bow to send bitter words flying like arrows to wound others. It describes them gathering in secret counsel in rebellion against the blameless, heartening and urging one another on in a shared evil purpose. Their work is deep and diligent scheming to lay hidden snares, followed by a sudden, fearless strike delivered in secret.

The verse belongs to a prophecy that will be literally fulfilled amid the shaking of all that can be shaken. That fulfillment will fall upon God's people when everything that can be shaken is shaken, in order that what cannot be shaken may remain, when the Lord has a pure and holy people who stand the test. God will meet the attack by turning their own speech back upon them to wound them, so that all who see flee away, and all people fear and declare the work of God and wisely consider His doing, while the righteous are glad in the Lord and put their trust in Him and all the upright in heart glory. In view of that coming fulfillment, every believer must now search his own heart closely.