כִּ֤י אֵ֪ין בְּפִ֡יהוּ נְכוֹנָה֮ קִרְבָּ֪ם הַ֫וּ֥וֹת קֶֽבֶר־פָּת֥וּחַ גְּרוֹנָ֑ם לְ֝שׁוֹנָ֗ם יַחֲלִֽיקוּן׃
For there is no sincerity in their mouth; Their inward part is a yawning gulf, Their throat is an open sepulchre; They make smooth their tongue.
Rashi on Psalms
For there is no sincerity in his mouth They appear as friends but they are enemies.
Radak on Psalms
For there is nothing straightforward in his mouth: – That is the reason why he says because of my watchful foes, for they are men of such a kind that there is no straightforwardness in the mouth (even) of one of them, but they make themselves appear to be friends.
Rashi on Psalms
there is malice in their heart Their thoughts are deceitful.