The Book of Malachi (or Malachias) is the last book of the Minor Prophets and the last book before the New Testament.  The book is often attributed to the prophet Malachi.  In Book of Malachi, Malachi corrects the lax religious and social behavior of the Israelites, particularly the corrupt behavior of priests, in post-exilic Jerusalem.  Book of Malachi was written around 535 BC, when the Persian Empire ruled the Promised Land.