John Calvin on Jeremiah 9:8

The Prophet again complains of the deceitfulness of their tongues; and he compares them to deadly, or drawn out arrows. Gold is said to be drawn out, when refined by repeated meltings; so also arrows, when sharpened, are more piercing. The Prophet then says, that their tongues were like deadly or sharpened arrows: how so? because they ever spoke guile, by either slandering or circumventing others. But the expression is general; and the Prophet no doubt meant to include all modes of deceiving.

For it afterwards follows, With the mouth they speak peace; that is, every one professed friendship, and his words were honey; and yet within he did set up, or concealed intrigues. Here in other words he sets forth their perfidy; for the tongue and the heart differed. They shewed by the tongue what was different from the sentiment of the heart. Hence he says, that they set up treacheries in the midst of them, or in their hearts, while they spoke peace with the mouth, that is, pretended brotherly kindness. The word, שוחט, means “killing” or slaying; see Genesis 22:10; Genesis 37:31; Exodus 12:6. Its primary meaning, as Parkhurst thinks, is to shed, or to drain off, either blood from animals, or juice from grapes, or gold from dross. But it is used in the sense of slaying. The Septuagint and the Vulgate render it here, “wounding,” —

A killing arrow is their tongue; Deceit it speaks; With his mouth does one speak peace to his neighbor, But in his heart he sets an ambush for him.

Literally, “his ambush,” that is, the ambush of which he is the object. This form of speech is often in Hebrew. See Job 28:10. “Penit ei insidias“ is the Vulgate. Blayney gives a paraphrase, not a version, —

But inwardly will he resolve to fall upon him by surprise.

The future tense here, as in many other instances, is used as a present tense, and designed to shew the habitual practice of the people. The same is done in the Welsh language: the future tense is continually used to express a present action. — Ed. At last he repeats again what he had said before, (Jeremiah 5:9) —

Jeremiah 9:9

9. Shall I not visit them for these things? saith the LORD: shall not my soul be avenged on such a nation as this?

9. An super hoc non visitabo eos, dicit Jehova? an in gente quae talis est (quae est sicut haec) non se ulciscetur anima mea?