Moses' first words of his address make plain that his words will really be God's words. Moses draws attention to the covenant character of Israel's God, that he is the "Lord our God." He then hastens to quote the word of the Lord, uttered at Horeb, now also relevant in the plains of Moab, that in order for Israel to fully realize its status as a nation, it needs to move on, until it possess the Promised Land.
6 “The LORD our God said to us in Horeb, ‘You have stayed long enough at this mountain.