Deuteronomy 31:24-26

24And it came to pass, when Moses had ended writing the words of this law in a book, until their conclusion,

25that Moses commanded the Levites, who bore the ark of the covenant of Jehovah, saying,

26Take this book of the law, and put it at the side of the ark of the covenant of Jehovah your 1God, that it may be there for a witness against thee;