For — The Lord turns now his speech from Israel to Judah. Break up — Prepare your hearts by making them soft, tender, and pliable, fit to embrace my word. A metaphor taken from plow — men. Thorns — Rid your hearts and hands of what may hinder you of embracing my word.
Related Commentaries of Jeremiah 4:3
Jeremiah 4:3
3 For thus saith the LORD to the men of Judah and Jerusalem, Break up your fallow ground, and sow not among thorns.