NOTES for Deu 2:1-37
During the journey from Sinai to the borders of the land promised by God, according to the testimony of the Book of Deuteronomy, the generation of those who came out of Egypt passed from life. Only after this, as God had said to Moses already at Sinai, does the process of conquering the land begin. It was, of course, not instantaneous, and the journey itself took a great deal of time. Moses was a little over eighty years old when God first revealed Himself to him at Sinai, and he died in the steppes of Transjordan at the age of one hundred twenty. Forty years passed from the day the people left Egypt before they were ready to enter the land promised by God to their fathers. For the ancient Hebrews, forty years was the span of one generation. More precisely, of course, not of life, but of active capacity; the age from twenty to sixty was considered such. Although it often turned out, as it did with Moses, that a person did the main work of his life while going far beyond the bounds of this "age of capacity."
In this case, one can speak of a whole generation leaving the stage, a generation that could be called the generation of the Exodus. Their children began the conquest of the land promised by God to the people, and it had to be completed not by the children, but by the grandchildren of those who left Egypt. The process of conquering the land stretched across three generations, of course not by accident. It is known that first-generation settlers, whether emigrants or returnees, still tend to look back; psychologically, they have not yet fully parted with their former homeland, apart from rare exceptions, which of course always exist. Their children, especially those born after the move, usually already feel themselves to be local residents, but still remember that they are children of newcomers, and that memory can leave its mark on their life and on their perception of reality. The grandchildren of those who moved to a new place, however, already feel themselves to be local residents fully and unconditionally; they have nowhere and no reason to return, even purely theoretically, and if they remember their origin, it is only at the level of certain everyday customs and national holidays, if they have anyone with whom to celebrate them.
This is the external, ethnopsychological side of the matter. There is another side as well, deeper and properly spiritual, connected nevertheless with the external side. God's work can be done only without looking back, whether at those around us or at our own past. To conquer the land, the people had to unlearn constantly looking back and remembering Egypt. That is why it was necessary to wait until the generation changed: the children and grandchildren of those who came out of Egypt were already ready to fight for their land without looking back, and in the same way, without looking back, to follow God.