Jeremiah 9:8 in the King James Version
Their tongue is as an arrow shot out; it speaketh deceit: one speaketh peaceably to his neighbour with his mouth, but in heart he layeth his wait.
Context
7 Therefore the LORD of Armies says, “Behold, I will melt them and test them; for how should I deal with the daughter of my people?
8 Their tongue is a deadly arrow. It speaks deceit. One speaks peaceably to his neighbor with his mouth, but in his heart, he waits to ambush him.
9 Shouldn’t I punish them for these things?” says the LORD. “Shouldn’t my soul be avenged on a nation such as this?