Psalm 12:2
"They speak vanity every one with his neighbour: with flattering lips and with a double heart do they speak."
Cross References (ranked by relevance)
For they that are such serve not our Lord Jesus Christ, but their own belly; and by good words and fair speeches deceive the hearts of the simple.
Their tongue is as an arrow shot out; it speaketh deceit: one speaketh peaceably to his neighbour with his mouth, but in heart he layeth his wait.
And if he come to see me, he speaketh vanity: his heart gathereth iniquity to itself; when he goeth abroad, he telleth it.
His mouth is full of cursing and deceit and fraud: under his tongue is mischief and vanity.
Whose mouth speaketh vanity, and their right hand is a right hand of falsehood.
For there is no faithfulness in their mouth; their inward part is very wickedness; their throat is an open sepulchre; they flatter with their tongue.
Draw me not away with the wicked, and with the workers of iniquity, which speak peace to their neighbours, but mischief is in their hearts.
A double minded man is unstable in all his ways.
For neither at any time used we flattering words, as ye know, nor a cloke of covetousness; God is witness:
A man that flattereth his neighbour spreadeth a net for his feet.
For there shall be no more any vain vision nor flattering divination within the house of Israel.
The words of his mouth were smoother than butter, but war was in his heart: his words were softer than oil, yet were they drawn swords.
They only consult to cast him down from his excellency: they delight in lies: they bless with their mouth, but they curse inwardly. Selah.
Rid me, and deliver me from the hand of strange children, whose mouth speaketh vanity, and their right hand is a right hand of falsehood:
He that goeth about as a talebearer revealeth secrets: therefore meddle not with him that flattereth with his lips.
For the sin of their mouth and the words of their lips let them even be taken in their pride: and for cursing and lying which they speak.
Of Zebulun, such as went forth to battle, expert in war, with all instruments of war, fifty thousand, which could keep rank: they were not of double heart.