The Book of Malachi is the last book of the Neviim contained in the Tanakh, canonically the last of the Twelve Minor Prophets. In most Christian orderings, the grouping of the prophetic books is the last section of the Old Testament, making Malachi the last book before the New Testament.
The whole Book of Malachi in Latin as a part of Codex Gigas, made around 13th century.
Illustration of the coming of God's Messenger in 3:1, by Franciszek Żmurko
Quotation from Malachi 3:1 in an Austrian church: "The Lord shall come to his temple."
The Minor Prophets or Twelve Prophets, occasionally Book of the Twelve, is a collection of prophetic books, written between about the 8th and 4th centuries BCE, which are in both the Jewish Tanakh and Christian Old Testament.
The first part of the book of Twelve Minor Prophets (the first book is the Book of Hosea) in the Codex Gigas, the largest extant medieval manuscript in the world, from 13th century. Now at the National Library of Sweden in Stockholm.
A high resolution scan of the Aleppo Codex containing parts of the Book of the Twelve Minor Prophets (the eighth book in Nevi'im), from 10th century.