Here's an accessible reference that aids personal Bible study or Sunday school preparation--the
Layman's Bible Commentary, reference for the everyday Christian, not the scholar Volume 11--covering Galatians through Philemon--provides section-by-section commentary on the flow and theme of each book, as well as historical and literary context for each. Major interpretations are presented for controversial passages and topics. Puzzling passages and Bible practices are explained, and charts and diagrams further aid your understanding. And "Take It Home" segments provide a practical application for each passage.
