Psalm 12:2

They talk of vanity every one with his neighbour; they do but flatter with their lips, and dissemble in their double heart.

Psalm 41:6

And if he come to see me, he speaketh vanity, and his heart conceiveth falsehood within himself; and when he cometh forth, he telleth it.

Romans 16:18

For they that are such serve not the Lord Jesus Christ: but their own bellies. And with sweet preachings and flattering words deceive the hearts of the innocents:

Psalm 10:7

His mouth is full of cursing, deceit and fraud; under his tongue is travail and sorrow.

Jeremiah 9:8

Their tongues are like sharp arrows, to speak deceit. With their mouth they speak peaceably to their neighbour, but privily they lay wait for him.

1 Chronicles 12:33

And of Zebulun that went out with the Host and proceeded in the array to battle with all manner of weapons of war, fifty thousand that kept in order with one accord.

Psalm 5:9

For there is no faithfulness in their mouths; they dissemble in their hearts. Their throat is an open sepulchre; they flatter with their tongue.

Psalm 28:3

O pluck me not away, neither destroy me with the ungodly and wicked doers, which speak friendly to their neighbours, but imagine mischief in their hearts.

Psalm 144:8

whose mouth talketh of vanity, and their righthand is a righthand of falsity.

James 1:8

A wavering minded man is unstable in all his ways.

Psalm 36:3-4

The words of his mouth are unrighteous and full of deceit; he hath left off to behave himself wisely, and to do good.

Psalm 38:12

They also that sought after my life laid snares for me; and they that went about to do me evil talked of wickedness, and imagined deceit all the day long.

Psalm 52:1-4

{To the Chanter, an exhortation of David when Doeg the Edomite came to Saul, and showed him, saying: David is come to the house of Abimelech} Thy boastest thou thyself, thou tyrant, that thou canst do mischief, whereas the goodness of God endureth yet daily?

Psalm 55:21

Their mouths are softer than butter, and yet have they battle in their mind: their words are smoother than oil, and yet be they very swords.

Psalm 59:12

For the sin of their mouth, for the words of their lips, and because of their pride, let them be taken. And why? Their preaching is of cursing and lies.

Psalm 62:4

Their device is only how to put him out, whom God will exalt; their delight is in lies. They give good words with their mouth, but curse with their heart. Selah.

Psalm 144:11

Save me, and deliver me from the hand of strange children, whose mouth talketh of vanity, and their righthand is a righthand of falsity -

Proverbs 20:19

Meddle not with him that betrayeth secrets, and is a slanderer, and deceiveth with his lips.

Proverbs 29:5

Whoso flattereth his neighbour, layeth a net for his feet.

Jeremiah 9:2-6

Would God that I had a cottage somewhere far from folk, that I might leave my people, and go from them: for they be all adulterers and a shrinking sort.

Ezekiel 12:24

There shall no vision be in vain, neither any prophecy fail among the children of Israel:

1 Thessalonians 2:5

Neither was our conversation at any time with flattering words - as ye well know - neither in cloaked covetousness, God is record:

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 faithfulness in their mouths; they dissemble in their hearts. Their throat is an open sepulchre; they flatter with their tongue.
Psalm 28:3
O pluck me not away, neither destroy me with the ungodly and wicked doers, which speak friendly to their neighbours, but imagine mischief in their hearts.
Psalm 62:4
Their device is only how to put him out, whom God will exalt; their delight is in lies. They give good words with their mouth, but curse with their heart. Selah.
Proverbs 20:19
Meddle not with him that betrayeth secrets, and is a slanderer, and deceiveth with his lips.
Proverbs 29:5
Whoso flattereth his neighbour, layeth a net for his feet.
Ezekiel 12:24
There shall no vision be in vain, neither any prophecy fail among the children of Israel:
Romans 16:18
For they that are such serve not the Lord Jesus Christ: but their own bellies. And with sweet preachings and flattering words deceive the hearts of the innocents:
1 Thessalonians 2:5
Neither was our conversation at any time with flattering words - as ye well know - neither in cloaked covetousness, God is record:

A double heart

1 Chronicles 12:33
And of Zebulun that went out with the Host and proceeded in the array to battle with all manner of weapons of war, fifty thousand that kept in order with one accord.

General references

Genesis 29:19
And Laban answered, "It is better that I give her thee, than to another man: bide therefore with me."
Judges 16:6
And Delilah said to Samson, "Oh, tell me where thy great strength lieth, and if thou were bound wherewith men might constrain thee."
Habakkuk 1:3
Why lettest thou me see weariness and labour? Tyranny and violence are before me, power overgoeth right:
Acts 12:22
And the people gave a shout, saying, "It is the voice of a god and not of a man."