Menachot 34 - Why Write the Mezuzah on a Scroll
But perhaps we should rather compare it to the writing of the words of the Torah on the stones, as the Jews did when on their entry to Israel? - We prefer to compare writing that applies in all generations (mezuzah) to writing that applies in all generations (Get), and not to writing which only happened once.
A better derivation is from the words "and you will write" (uchtavtam) themselves, which can be translated as "complete writing" - that is, on the scroll, and not on the stones. Now that we have this direct derivation, what do we need the previous one for? - You might still think to engrave the words on a stone, then attach the stone to the doorpost. This teaches otherwise.
Art: Laurent de La Hyre - Moses and the Tablets of the Law
