Nahum was an Old Testament prophet and the book of Nahum is part of the Old Testament. The book of Nahum is a prophetic book that contains the words of the prophet Nahum, who lived in the 7th century BC. It is believed to have been written in the city of Nineveh, which was destroyed by the Babylonians in 612 BC. The book of Nahum is a short book, consisting of only three chapters. It is mainly concerned with the destruction of Nineveh and the fall of the Assyrian Empire.