(Proverbs 4:24): "Remove from yourself crookedness of mouth" - this is evil speech, which is as severe as the shedding of blood. "And put the deviousness of lips far from you" - that you should not speak with your fellow one thing with the mouth and another in the heart.
Remove Crooked Speech And Keep Your Lips From Deceit
Midrash Mishlei 4:2
(משלי ד כד): "הסר ממך עקשות פה" - זה לשון הרע, שהוא קשה כשפיכות דמים. "ולזות שפתיים הרחק ממך" - שלא תהא מדבר עם חברך אחד בפה ואחד בלב.