In Baruch 6, the book concludes with a letter, which is comparable to, but different then Jeremiah’s letter recorded in Jeremiah 29. Also, Jeremiah 10:2-15 contains some similar language to Baruch 6. Some versions of the Bible pull out Baruch 6 and include it as a separate one-chapter book, called the Letter of Jeremiah or the Epistle of Jeremiah.
Baruch is an Apocrypha book and not included in all versions of the Bible. The New Jerusalem Bible, Revised Standard Version (RSV), New American Bible (NABRE), Wycliffe Bible (WYC), Common English Bible (CEB), Good News Translation (GNT), and Douay-Rheims (DRA) all include Baruch. Interestingly, the original Authorized King James Version (KJV) contains Baruch, but the text was removed almost two centuries later. The Septuagint, an ancient Greek translation of the Jewish scriptures, which was widely used in Jesus’s day, also includes the book of Baruch.
For more information, see why “Christians Should Consider the Entire Bible.”