Proverbs 26.25

When he speaketh fair, believe him not: for there are seven abominations in his heart.

Proverbs 20.19

He that goeth about as a talebearer revealeth secrets: therefore meddle not with him that flattereth with his lips.

Psalm 12.2-3

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

3 The LORD shall cut off all flattering lips, and the tongue that speaketh proud things: