לזכות ר' אברהם יצחק בן אסתר וכל בני ביתו
The Rambam says that the Torah alludes to the fact that we must believe in the coming of Moshiach when it says ואם ירחב השם את גבולך ויספת שלש ערים - If Hashem expands your borders, you should add three cities as ערי מקלט. Since this has never happened and the Torah is eternal, it must be referring to the time when Moshiach comes.
The question is that the gemara says that there was never a Ben Sorer Umoreh and the only reason the Torah writes about it is דרוש וקבל שכר - for academic purposes. So why can't we say the same thing about adding three cities - it will never happen and the Torah writes it for academic purposes דרוש וקבל שכר? So no proof....
וצ"ע - הרבי מחב"ד כתב שאולי אפשר לחלק וצ"ע
[Don't worry - we have other pesukim from the Torah and Neviim to prove that Moshiach will come].