Deut. 29:2-6 says:
And Moses called unto all Israel, and said unto them, Ye have seen all that the LORD did before your eyes in the land of Egypt unto Pharaoh, and unto all his servants, and unto all his land; The great temptations which thine eyes have seen, the signs, and those great miracles: Yet the LORD hath not given you an heart to perceive, and eyes to see, and ears to hear, unto this day. And I have led you forty years in the wilderness: your clothes are not waxen old upon you, and thy shoe is not waxen old upon thy foot. Ye have not eaten bread, neither have ye drunk wine or strong drink: that ye might know that I am the LORD your God.
Is Moses saying that he is the LORD their God? Not really -- let's do something to clarify matters:
Ye have not eaten bread, neither have ye drunk wine or strong drink: that ye might know that "I am the LORD your God."
Quotations marks hadn't been invented yet, but there is every reason to think that we need them here to understand what is going on. Moses is appealing to a saying repeated over and over again (starting in Exodus 6:7, and thereafter many times in Leviticus, and once in Numbers) affirming the supremacy of God. Here, now, he reminds the Israelites of what they have seen and experienced, and the reason for it -- and he uses a powerful, stereotypical phrase to remind them.
This is just the sort of verbal performance we would expect from an oral-based society.
-JPH