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From this week's sedra (Shmot 16:35):
And the children of Israel did eat the manna forty years, until they came to a land inhabited; they did eat the manna, until they came unto the borders of the land of Canaan
However at the time, the Israelites had not sinned with the incident of the spies, as this would happen on the 9th of Av on the 2nd year, so 1 year and 3 months later approximately. And so the manna would only originally have been for this period of time?
Was Moshe told to "edit in" this posuk later?