For the priests who bore the ark stood in the midst of the Jordan, until everything was finished that Yahweh commanded Joshua to speak to the people, according to all that Moses commanded Joshua: and the people hurried and passed over.
The immense importance of the ark of the covenant also shines in passages such as this.  And where, pray tell, did this ark of the covenant come from?  It is starkly clear to every student of the Bible that Joshua is but a continuation of the historical books called the Pentateuch.  If one wishes to know all about the ark of the covenant, he may surely read it in the Five Books of Moses, and it is no wonder that Moses' successor was the official custodian of that ark and all that it represented.