Be thou instructed - Be thou chastised: learn the lesson which chastisement is intended to teach thee.
Lest my soul - Lest I Myself - not “depart from thee,” God does not willingly leave His people, but - “be torn from thee.”
Related Commentaries of Jeremiah 6:8
Jeremiah 6:8
8 Be thou instructed, O Jerusalem, lest my soul departc from thee; lest I make thee desolate, a land not inhabited.