Deuteronomy 31:9

9. And Moses wrote this law This law need not mean the whole of the book of Deuteronomy, but only the most important part. At this time it was formally handed over to the priests for safe keeping.

Which bare the ark of the covenant It was the province of the Kohathites to carry the ark and its furniture. See Numbers 4:15. It would seem that on special occasions the priests performed the office of bearing the ark, as in the passage through Jordan (Joshua 3:3; Joshua 4:9) and around Jericho, (Joshua 6:6,) and in the solemn proclamation of the law at Ebal and Gerizim, and in the dedication of the temple. 1 Kings 8:3.

And unto all the elders The priests represented the ecclesiastical polity and the elders the civil polity of Israel. In these two bodies the whole nation was represented.