"Moses assigned the priests and elders the duty of regularly republishing the law of the covenant. The effect of this was to associate the priests and elders with Joshua in the responsibility of rule and in the esteem of Israel. More important, all the covenant people, together with all human authorities in the covenant community, were placed under the lordship of the Giver of the law." [1][source]
Before he died, Moses left a written document with the leaders of the nation that the Israelites regarded as God"s law ( Deuteronomy 31:9, cf. Joshua 1:8). This probably refers to Moses" exposition of the law (chs5-26), though the exact meaning of the "law" (torah, instruction, Deuteronomy 31:9; Deuteronomy 31:24) here is not clear. [source][source][source]
The national leaders were to read this law to the whole nation every seventh (sabbatical) year at the Feast of Booths (Tabernacles). This reading would remind and instruct God"s people concerning His gracious will for them. It was common in other ancient Near Eastern countries for the priests to assemble the people periodically and read them the king"s covenant (cf. Deuteronomy 16:13-17). [source][source][source]