Here it is the LORD who is speaking about his people, as Good News Translation makes clear. It is not natural to have the LORD’s statement begin with For, since there is nothing he just said to connect this to. Consequently, a word such as “Well” is a better rendering, although many translations (for example Good News Translation) simply drop it.
Foolish (used only here in Jeremiah) is a favorite term in the book of Proverbs, where it is the opposite of “wise.” Translators can may express this as “My people are fools” (so New International Version) if that would be more natural.
Know me: See “I knew you” in 1.5. In the Hebrew text me is placed in the emphatic position. The idea here really is that the people had no relationship with God. Translators can say, for example, “they don’t know who I am,” “they know nothing about me,” “they have no relationship with me,” “they are not my people,” or “they do not know me as their God.”
Stupid is used again in 5.21 (Revised Standard Version “foolish”); elsewhere it occurs in the Old Testament only in Ecclesiastes (2.19; 7.17; 10.3, 14). In Hebrew there is apparently a play on words between children and understanding. However, it is doubtful if this may be maintained in translation. It is really quite difficult to distinguish among these things the LORD says about the people of Israel: foolish, stupid, no understanding. Translators should choose three terms that a parent or schoolteacher might use when scolding children, such as “foolish,” “no sense at all,” “stupid,” and “blockheads.”
Skilled: See also 8.8; 9.12, 17; 10.7, 9; 18.18; 50.35; in these passages Revised Standard Version often has “wise.” Revised English Bible translates “clever” and New Jerusalem Bible “clever enough.”
But how to do good they know not is rather awkward in English. Good News Translation restructures the last sentence of this verse as “They are experts at doing what is evil, but failures at doing what is good.” Die Bibel im heutigen Deutsch, freely translated, is “They know well how to do evil, but to do good is beyond their understanding.”
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 .