Parshat Ki Tavo: That's A Lot of Chiseling!

As part of his farewell speech to Bnei Yisrael, Moshe informed the people of a mitzvah they were to perform once they crossed the Jordan (Devarim 28:2-3)

והיה ביום אשר תעברו את הירדן אל הארץ אשר ה' אלוקיך נתן לך והקמת לך אבנים גדולות ושדת אתם בשיד. וכתבת עליהן את כל דברי התורה הזאת בעברך למען אשר תבא אל הארץ אשר ה' אלוקיך נתן לך ארץ זבת חלב ודבש כאשר דבר ה' אלוקי אבותיך לך
It shall be on the day that you cross the Jordan to the Land that Hashem, your God, gives you, you shall set up great stones and you shall coat them with plaster. You shall inscribe on them all the words of this Torah, when you cross over, so that you may enter the Land that Hashem, your God, gives you, a Land flowing with milk and honey, as Hashem, the God of your forefathers, spoke about you.

In explaining the purpose of this mitzvah, Rabbi Don Isaac Abrabanel, writes that it was the custom of all conquerors to place monuments and symbols throughout the lands which they had conquered to show their strength and to let it be known that they ruled the land; He writes that this was in fact the practice employed by the Romans whenever they conquered a new land. Similarly, in the modern day the United States planted a flag on the moon to show that they were the first to land on the moon.

With His people ready to conquer the Land which He had promised to their forefathers, Hashem decided that they should demonstrate their might to the inhabitants of the Land; instead of raising a flag or erecting a statue of a king, Bnei Yisrael were charged to build a monument that would show the whole world the source of their strength and success - the Torah.
There is a difference of opinion amongst the commentators as to what was written on the stones. Ibn Ezra quotes Rav Saadiah Gaon who explains that Bnei Yisrael were not required to write the entire text of the Torah on the stones, but rather a listing of the mitzvot. However, it seems from a literal reading of the text, "You shall inscribe on them all the words of the Torah," that Bnei Yisrael were commanded to write the entire Torah beginning with Breishit and ending with the conclusion of Sefer Devarim. The Gemara (Sotah 32a) explains that not only did they have to write the entire Torah, but it had to be written as the Torah says (Devarim 27:8), "well clarifed", which Chazal interpret to mean, all spoken languages.
If one takes the position that the entire Torah had to be written on the stones and that it had to be written in all spoken languages, seventy in total, it would seem that Bnei Yisrael were given a task that would take generations to complete! In fact the Ramban (27:3) writes,

ויתכן שהיו האבנים גדולות מאד, או שהיה ממעשה הנסים
And it would follow that they had extremely large stones, or that there was a miraculous act

A rational approach to this dilemma is offered by Rabbi Yaakov Tzvi Mecklenburg (1785-1865) in his work, Ha'ketav V'HaKabblah. Rabbi Mecklenburg writes that when it comes to the mitzvah of mezuzah the Torah tells us (Devarim 6:9),

וכתבתם על מזוזות ביתך ובשעריך
And write them on the doorposts of your house and upon your gates

We know that the Torah does not mean that we should literally write the text of the Shema on our doorposts. Rather, we are required to write it on a piece of parchment and place the parchment on our doorposts. So too, writes Rabbi Mecklenburg, God did not command the people to literally write, or in this case chisel, the words of the Torah onto the stones. Rather, they could write it on parchment and place the parchment onto the stones, thus making this mitzvah a much less time consuming. Perhaps this is the reason why God also commanded the people to cover the stones with plaster - in order to protect the parchment from being damaged by the elements so that they could be an eternal reminder of our true source of strength.