Psalm 12:2

Everyone lies to his neighbor. They speak with flattering lips, and with a double heart.

Psalm 41:6

If he comes to see me, he speaks falsehood. His heart gathers iniquity to itself. When he goes abroad, he tells it.

Romans 16:18

For those who are such don't serve our Lord, Jesus Christ, but their own belly; and by their smooth and flattering speech, they deceive the hearts of the innocent.

Psalm 10:7

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

Jeremiah 9:8

Their tongue is a deadly arrow; it speaks deceit: one speaks peaceably to his neighbor with his mouth, but in his heart he lays wait for him.

1 Chronicles 12:33

Of Zebulun, such as were able to go out in the army, who could set the battle in array, with all kinds of instruments of war, fifty thousand, and who could order [the battle array, and were] not of double heart.

Psalm 5:9

For there is no faithfulness in their mouth. Their heart is destruction. Their throat is an open tomb. They flatter with their tongue.

Psalm 28:3

Don't draw me away with the wicked, with the workers of iniquity who speak peace with their neighbors, but mischief is in their hearts.

Psalm 144:8

whose mouths speak deceit, Whose 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 iniquity and deceit. He has ceased to be wise and to do good.

Psalm 38:12

They also who seek after my life lay snares. Those who seek my hurt speak mischievous things, and meditate deceits all day long.

Psalm 52:1-4

Why do you boast of mischief, mighty man? God's loving kindness endures continually.

Psalm 55:21

His mouth was smooth as butter, but his heart was war. His words were softer than oil, yet they were drawn swords.

Psalm 59:12

For the sin of their mouth, and the words of their lips, let them be caught in their pride, for the curses and lies which they utter.

Psalm 62:4

They fully intend to throw him down from his lofty place. They delight in lies. They bless with their mouth, but they curse inwardly. Selah.

Psalm 144:11

Rescue me, and deliver me out of the hands of foreigners, whose mouths speak deceit, whose right hand is a right hand of falsehood.

Proverbs 20:19

He who goes about as a tale-bearer reveals secrets; therefore don't keep company with him who opens wide his lips.

Proverbs 29:5

A man who flatters his neighbor spreads a net for his feet.

Jeremiah 9:2-6

Oh that I had in the wilderness a lodging place of wayfaring men; that I might leave my people, and go from them! for they are all adulterers, an assembly of treacherous men.

Ezekiel 12:24

For there shall be no more any false vision nor flattering divination within the house of Israel.

1 Thessalonians 2:5

For neither were we at any time found using words of flattery, as you know, nor a cloak of 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 faithfulness in their mouth. Their heart is destruction. Their throat is an open tomb. They flatter with their tongue.
Psalm 28:3
Don't draw me away with the wicked, with the workers of iniquity who speak peace with their neighbors, but mischief is in their hearts.
Psalm 62:4
They fully intend to throw him down from his lofty place. They delight in lies. They bless with their mouth, but they curse inwardly. Selah.
Proverbs 20:19
He who goes about as a tale-bearer reveals secrets; therefore don't keep company with him who opens wide his lips.
Proverbs 29:5
A man who flatters his neighbor spreads a net for his feet.
Ezekiel 12:24
For there shall be no more any false vision nor flattering divination within the house of Israel.
Romans 16:18
For those who are such don't serve our Lord, Jesus Christ, but their own belly; and by their smooth and flattering speech, they deceive the hearts of the innocent.
1 Thessalonians 2:5
For neither were we at any time found using words of flattery, as you know, nor a cloak of covetousness (God is witness),

A double heart

1 Chronicles 12:33
Of Zebulun, such as were able to go out in the army, who could set the battle in array, with all kinds of instruments of war, fifty thousand, and who could order [the battle array, and were] not of double heart.

General references

Genesis 29:19
Laban said, "It is better that I give her to you, than that I should give her to another man. Stay with me."
Judges 16:6
Delilah said to Samson, "Please tell me where your great strength lies, and what you might be bound to afflict you."
Habakkuk 1:3
Why do you show me iniquity, and look at perversity? For destruction and violence are before me. There is strife, and contention rises up.
Acts 12:22
The people shouted, "The voice of a god, and not of a man!"