Moshe is the Last Word

Gemara: Is it so [that there was a change in the Torah’s letters]? Doesn’t the Torah say, "These are the mitzvot," from which we learn that a prophet is not allowed to present anything new from that point?

Ein Ayah: The same lofty source from which elevated prophecy comes and from which permanent mitzvot come, is the foundation of the knowledge that no new mitzvot are going to come in the future. Only the trustworthy shepherd (i.e., Moshe) was chosen from way back in time to gaze into the lit mirror from which permanent mitzvot come to the world.

When Moshe’s visions were completed, it was no longer possible for new mitzvot to be added or to be renewed. The same level of revelation and openness that is found in the Torah as we received it is as special as the hidden divine messages, and they are of the same nature. They cannot therefore appear in revealed form [based on prophecy] after the wondrous and special revelation [to Moshe]. In fact, these are the mitzvot, and no prophet can add to them.