Deuteronomy 31 marks a turning point in leadership. Moses, 120 years old, could no longer go out and come in, and God had said he would not cross the Jordan. Yet he assured Israel that Yahweh himself would go before them to destroy the nations, and that Joshua would lead them over. The charge, Be strong and courageous, rested not on Israel's strength but on God's presence: he will not fail you nor forsake you. Hebrews 13:5 applies this promise to all believers.
Moses wrote the law and entrusted it to the Levitical priests and elders. Every seventh year, at the Feast of Booths, it was to be read before all Israel, men, women, little ones, and foreigners, so that they may hear, learn to fear Yahweh, and observe it. Their children, who had not known, would also learn. Public reading of Scripture was central to Israel's faith, as it remains in the church (1 Timothy 4:13).
At the Tent of Meeting, God appeared in a pillar of cloud and told Moses plainly that Israel would turn to other gods. God commanded Moses to write a song and teach it, so that when troubles came, the song would testify against them as a witness. Moses commissioned Joshua, then gave the completed book of the law to the Levites to place beside the ark of the covenant. God's word would outlast its human messenger.