Which book completed the Old Testament?
The book of Malachi completed the Old Testament. After Malachi was written, 400 years of silence elapsed until God's next move with Israel, when an angel announced the birth of John the Baptist and appeared to Joseph and Mary. Malachi is the final Old Testament book.
Les explains that between the book of Malachi and the appearance of the angel announcing the birth of John the Baptist and to Joseph and Mary is 400 years, which he calls the 400 years of silence. Up until that time, from Abraham until Malachi, God had been revealing Himself through the prophets and through various other means to the nation of Israel. But after the book of Malachi was written, completing the Old Testament, 400 years elapsed until God makes His next move with the nation of Israel. Les presents this as a historical fact that he finds interesting.