The Letter of Jeremiah, or the Epistle of Jeremiah, is a note of encouragement written by Jeremiah and sent to the exiles living in Babylon. The theme of the letter reminds the Jews in Babylon to avoid idols and idol worship.
Some versions of the Bible include the Letter of Jeremiah as an addendum to the book of Baruch, in Baruch 6. This includes the original Authorized King James Version (KJV), The New Jerusalem Bible, New American Bible (NAB), Good News Translation (GNT) and Douay-Rheims (DRA). Though Baruch did not write the letter, he may have preserved it and added it to his other writings. This is understandable, since Baruch was the scribe who helped Jeremiah record the prophet’s writings for the book of Jeremiah.
The Letter of Jeremiah is an Apocrypha book and not included in all versions of the Bible. The Common English Bible (CEB), Revised Standard Version (RSV), and Wycliffe Bible (WYC) all include the Letter of Jeremiah. The Eastern Orthodox and Ethiopian Churches have the Letter of Jeremiah in their scriptures.
For more information, see why “Christians Should Consider the Entire Bible.”