Deuteronomy 31:9-13 - Moses wrote down this Law

31:9-11

Moses wrote down the Law, this is presumably the material in Deuteronomy, i.e. the second giving of the Law. It was then given to the priests who carried the ark of the covenant. At the end of every seven years the Law was to be read out to all the people. This would remind them of how they should live. This was also the year for cancelling debts, so it would remind them why they were doing such a crazy thing.

31:12,13

The people were to be assembled  so that they could listen to the Law. They were to learn to fear the Lord and to obey Him. This applied to everyone, men, women, children and foreigners residing in the land. The Law was to be passed onto future generations. For children would not know the Lord unless they heard it and were taught it.