Charles Ellicott Commentary Exodus 25:16

"And thou shalt put into the ark the testimony which I shall give thee." — Exodus 25:16 (ASV)

The testimony which I shall give thee. —The two tables of stone were called “the Testimony” , as being God’s witness against sin (Deuteronomy 31:26). As containing them, the ark was called “the ark of the testimony” (Exodus 25:22; Exodus 26:34; Exodus 30:6; Exodus 30:26, and so on; Numbers 4:5; Numbers 7:89; Joshua 4:16).