Psalm 12:2

They speak falsehood every one with his neighbour: with flattering lip, with a double heart, do they speak.

Psalm 41:6

And if one come to see me, he speaketh falsehood; his heart gathereth wickedness to itself: he goeth abroad, he telleth it.

Romans 16:18

For such serve not our Lord Christ, but their own belly, and by good words and fair speeches deceive the hearts of the unsuspecting.

Psalm 10:7

His mouth is full of cursing, and deceit, and oppression; under his tongue is mischief and iniquity.

Jeremiah 9:8

Their tongue is a murderous arrow; it speaketh deceit. A man speaketh peaceably to his neighbour with his mouth, but in his heart he layeth his ambush.

1 Chronicles 12:33

Of Zebulun, such as went forth in the host, armed for war with all weapons of war, fifty thousand, keeping rank without double heart.

Psalm 5:9

For there is no certainty in their mouth; their inward part is perversion, their throat is an open sepulchre; they flatter with their tongue.

Psalm 28:3

Draw me not away with the wicked, and with the workers of iniquity, who speak peace to their neighbours, and mischief is in their heart.

Psalm 144:8

Whose mouth speaketh vanity, and their right hand is a right hand of falsehood.

James 1:8

he is a double-minded man, unstable in all his ways.

Psalm 36:3-4

The words of his mouth are wickedness and deceit: he hath left off to be wise, to do good.

Psalm 38:12

And they that seek after my life lay snares for me; and they that seek my hurt speak mischievous things, and meditate deceits all the day long.

Psalm 52:1-4

{To the chief Musician: an instruction. Of David; when Doeg the Edomite came and told Saul, and said unto him, David came to the house of Ahimelech.} Why boastest thou thyself in evil, thou mighty man? The loving-kindness of God abideth continually.

Psalm 55:21

Smooth were the milky words of his mouth, but his heart was war; his words were softer than oil, yet are they drawn swords.

Psalm 59:12

Because of the sin of their mouth, the word of their lips, let them even be taken in their pride; and because of cursing and lying which they speak.

Psalm 62:4

They only consult to thrust him down from his excellency; they delight in lies; they bless with their mouth, but in their inward part they curse. Selah.

Psalm 144:11

Rescue me, and deliver me from the hand of aliens, whose mouth speaketh vanity, and their right hand is a right hand of falsehood.

Proverbs 20:19

He that goeth about talebearing revealeth secrets; therefore meddle not with him that openeth his lips.

Proverbs 29:5

A man that flattereth his neighbour spreadeth a net for his steps.

Jeremiah 9:2-6

Oh that I had in the wilderness a traveller's lodging-place, that I might leave my people, and go away from them! For they are all adulterers, an assembly of treacherous men.

Ezekiel 12:24

For there shall be no more any vain vision nor flattering divination in the midst of the house of Israel.

1 Thessalonians 2:5

For we have not at any time been among you with flattering discourse, even as ye know, nor with a pretext for covetousness, God is witness;

Treasury of Scripture Knowledge

Summary

They speak vanity every one with his neighbour: with flattering lips and with a double heart do they speak.

A double heart

Bible References

Flattering

Psalm 5:9
For there is no certainty in their mouth; their inward part is perversion, their throat is an open sepulchre; they flatter with their tongue.
Psalm 28:3
Draw me not away with the wicked, and with the workers of iniquity, who speak peace to their neighbours, and mischief is in their heart.
Psalm 62:4
They only consult to thrust him down from his excellency; they delight in lies; they bless with their mouth, but in their inward part they curse. Selah.
Proverbs 20:19
He that goeth about talebearing revealeth secrets; therefore meddle not with him that openeth his lips.
Proverbs 29:5
A man that flattereth his neighbour spreadeth a net for his steps.
Ezekiel 12:24
For there shall be no more any vain vision nor flattering divination in the midst of the house of Israel.
Romans 16:18
For such serve not our Lord Christ, but their own belly, and by good words and fair speeches deceive the hearts of the unsuspecting.
1 Thessalonians 2:5
For we have not at any time been among you with flattering discourse, even as ye know, nor with a pretext for covetousness, God is witness;

A double heart

1 Chronicles 12:33
Of Zebulun, such as went forth in the host, armed for war with all weapons of war, fifty thousand, keeping rank without double heart.

General references

Genesis 29:19
And Laban said, It is better that I give her to thee than that I should give her to another man: abide with me.
Judges 16:6
And Deli'lah said to Samson, "Please tell me wherein your great strength lies, and how you might be bound, that one could subdue you."
Habakkuk 1:3
Why dost thou cause me to see iniquity, and lookest thou upon grievance? For spoiling and violence are before me; and there is strife, and contention riseth up.
Acts 12:22
And the people cried out, A god's voice and not a man's.