beside the ark: Unlike the stone tablets, they must place the scroll of Deuteronomy near the ark of the covenant, not inside it. It was kept in the inner sanctuary of the tabernacle and later in the temple (see 31:9; Exodus 25:16; 26:33).
a witness: Like the song the Israelites were required to sing, the scroll of Deuteronomy served as a constant reminder of Israel's covenant obligations and privileges (see Deuteronomy 31:19; see 31:10, 19).