וְאִ֤ישׁ בְּרֵעֵ֙הוּ֙ יְהָתֵ֔לּוּ וֶאֱמֶ֖ת לֹ֣א יְדַבֵּ֑רוּ לִמְּד֧וּ לְשׁוֹנָ֛ם דַּבֶּר־שֶׁ֖קֶר הַעֲוֵ֥ה נִלְאֽוּ׃
And they deceive every one his neighbour, And truth they speak not; They have taught their tongue to speak lies, They weary themselves to commit iniquity.
Read kabbalistic (mystical) interpretation of Jeremiah 9:4: and classical mystical sources.