Charles Ellicott Commentary Joshua 3:11

"Behold, the ark of the covenant of the Lord of all the earth passeth over before you into the Jordan." — Joshua 3:11 (ASV)

The ark of the covenant. —The ten commandments are presented throughout this narrative as a covenant. So Exodus 34:28, the words of the covenant, the ten commandments. It must be remembered that a promise precedes all the commandments: I am Jehovah your God. The “ten words” that follow are the testimony to His character who commanded the covenant. (See Silver Sockets, p. 28.)

The thing signified by the dividing of Jordan does indeed exhibit the law as a covenant in a way that those who followed Joshua can hardly have conceived. But history must come before prophecy, if prophecy is to be understood.