In the Seder HaDoros, published by R' Yechiel Heilprin in 1747, the author describes the life and legacy of many Jewish historical personalities including Rambam.
I'm not sure how historically accurate this book is considered to be, as many of the stories I read through seemed exaggerated and unlikely to be an objective portrayal of what events actually occurred. One example is the description of the Rambam being a beaten child who left home and stumbled upon the Ri MiGash whereupon he became a light to the nation. The Ri Migash died when the Rambam was seven, not leaving much time to study together. Another example would be the attribution of the צוואת הרמב"ם to Rambam, whereas we now know this to be untrue.
Anyway, the author lists the Rambam's works, and writes at the bottom of the right-hand column on עמוד נד/ב:
פי' על התורה מובא בכנסת הגדולה
I am interested in following the trail behind this story. This line is a bit cryptic to me. Is the author saying that the commentary is brought down in a Sefer called כנסת הגדולה? If so, does anyone have information on this Sefer?
Furthermore, I have never seen this claim being made elsewhere. Are there any other references to a commentary the Rambam may have written on the Torah? There is a Sefer that claims to be the Rambam's commentary on Esther, but this is generally seen to be an unsubstantiated claim.