The commandment to set up stones and to write the Torah is given by Moshe to the children of Israel twice. These appear to be two separate commandments and not simply a repetition of the same one.
What can we learn from this double commandment? Are the two sets of stones identical?
There are two possible explanations:
Just as a monument was set up to commemorate the Covenant on the one side of the Jordan, so too there also has to be a similar monument on the other side. The stones on the eastern side of the Jordan were also plastered with lime so that the two sets of stone would be identical, even though this was not actually necessary. For this same reason, the Tribes on the eastern side of the Jordan will set up an altar which was similar to the one in the Mishkan so that they would retain their connection to the Mishkan.
There was indeed a difference between the two sets of stones which symbolizes the difference between the Torah given in the wilderness and the Torah of Eretz Yisrael. In the wilderness the Torah was given on an ongoing basis through Moshe and the Mishkan. Upon entry to Eretz Yisrael, the authority to pass on the Torah was transferred to the children of Israel. For this reason, the instructions for the first set of stones was to write 'the words of the Torah', whereas in the instructions given for the second set (v.8) Moshe added the words 'very clearly'. When the first set of stones were set up, the words of the Torah could not be explained clearly because this authority was vested in God alone. However, following their entry to Eretz Yisrael, this authority was now transferred to the children of Israel.