Commentary for Jeremiah 9:7

Their tongue is a deadly arrow Heb. שחוט, drawn. Comp. (I Kings 10:16) “malleable gold” (שחוט). Also, (Hos. 5:2) “And the extent of their turning away (ושחטה),” (tirer in French), pulling. Another explanation is that it is actually an expression of slaughter (tranchant in French, cutting). In this manner Menahem classified it (Machbereth Menahem p. 172), and in this manner Jonathan rendered it: כּגיר די מחרף, like a sharpened arrow.

but in his heart lit. in his midst. Jonathan renders: in his innards.