THE LAW OF MOSES -(written on paper, placed outside the ark)
Deuteronomy 31: 24-26 And it came to pass, when Moses had made an end of writing the words of this law in a book, until they were finished, That Moses commanded the Levites, which bare the ark of the covenant of the Lord, saying, Take this book of the law, and put it in the side of the ark of the covenant of the Lord your God, that it may be there for a witness against thee.

TEN COMMANDMENTS- (written on stone, placed inside the ark)
Exodus 31:18 "And he gave unto Moses, when he had made an end of communing with him upon mount Sinai, two tables of testimony, tables of stone, written with the finger of God.
Exodus 40:20 "And he took and put the testimony into the ark, and set the staves on the ark, and put the mercy seat above upon the ark:"