Psalm 55:21
"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."
Cross References (ranked by relevance)
My soul is among lions: and I lie even among them that are set on fire, even the sons of men, whose teeth are spears and arrows, and their tongue a sharp sword.
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 lying tongue hateth those that are afflicted by it; and a flattering mouth worketh ruin.
Who whet their tongue like a sword, and bend their bows to shoot their arrows, even bitter words:
They speak vanity every one with his neighbour: with flattering lips and with a double heart do they speak.
Then Judas, which betrayed him, answered and said, Master, is it I? He said unto him, Thou hast said.
There is that speaketh like the piercings of a sword: but the tongue of the wise is health.
They only consult to cast him down from his excellency: they delight in lies: they bless with their mouth, but they curse inwardly. Selah.
And supper being ended, the devil having now put into the heart of Judas Iscariot, Simon’s son, to betray him;
Behold, they belch out with their mouth: swords are in their lips: for who, say they, doth hear?