Malachi is the last book of the Old Testament and is a book of Prophetic Oracle. It is a post-exilic book, meaning it was written after the return from captivity in Babylon. The prophet Malachi wrote it approximately 430 B. C. Key personalities include Malachi and the priests. The purpose of this book is that Malachi wrote to ensure that the hearts of the Jews was right and that they were keeping God first in their lives.