Jeremiah 9:8 in the World English Bible
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.
Context
7 Therefore thus saith the LORD of hosts, Behold, I will melt them, and try them; for how shall I do for the daughter of my people?
8 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.
9 Shall I not visit them for these things? saith the LORD: shall not my soul be avenged on such a nation as this?