For this can be “On this account” or “This is why.”

The LORD now calls the earth and the heavens (better “the sky”) to mourn because of the great destruction that he intends to bring upon it. However, translators should not use an imperative here. A simple future as in Good News Translation (“will mourn … will grow dark”) is better. Be black is better rendered “grow dark” (Good News Translation). The verb is used of the sun and moon in Joel 2.10, and of the day in Micah 3.6. In Jer 8.21 and 14.2 the meaning is “mourn/lament” (with reference to the dirty, uncared-for clothes that mourners wore).

So as to emphasize the LORD’s determination to bring about this destruction, the Hebrew writer uses four verbs together: spoken … purposed … not relented … nor … turn back. Translators who feel that I have spoken leaves some meaning out may need to say something like “I have said what I will do.” Revised English Bible combines the first two verbs and translates “for I have made known my purpose.” Another way to express the meaning is “I have made up my mind, and stated my decision.” The only other occurrence of the verb purposed in Jeremiah is found in 51.12, where Revised Standard Version translates “planned.” “Made his decision” (Good News Translation) or “decided what I will do” are also possible. Relented has as its primary meaning “regret” or “be sorry,” but in this context, Good News Translation “will not change his mind” is much better. “Will not retract his decree” and “will not change his decision” are also possible. Nor will I turn back also refers to going back on his decision. “I will not go back on my decision [or, on what I said I would do]” is an acceptable translation. The order of the verbs in the Septuagint differs slightly, as may be seen from New American Bible: “I have spoken, I will not repent, I have resolved, I will not turn back” (so also New International Version, Good News Translation, New Jerusalem Bible, Bright, Moffatt).

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on Jeremiah. (UBS Helps for Translators). New York: UBS, 2003. For this and other handbooks for translators see here .