In Yeshiva, I remember learning, that it is asur to say someone is the Mosheiach and/or to follow someone as if they are the Mosheiach.
A friend just told me that they learned the opposite and in fact that one must think that his Rebbe is the Mosheiach and consider him to be the Mosheiach.
Which is correct?
Klal Yisroel has been in Galus for more than 2000 years, and we still believe that although we don’t know who how or when, but we believe that moshiach will eventually come and bring the world to it ultimate goal, as stated numerous times in Tanach. The gemorta brings that there was only one instance when some of Klal Yisroel thought that someone was Moshiach. That was after the destruction of the second Temple, that R’ Akiva thought that (Midrash Eicha 2-4) Bar Kochba was the Moshiach. Other than that there is no place that i know of in Shulchan Aruch of the Rambam, that says that everyone has to believe that his Rebbe is Moshiach. In fact every hundred of so years there are people that get uip and make a claim that they are Moshiach, and after it is proven incorrect it just causes depression and damage to those who thought so. For example the story of Shabsai Tzvi, which caused a lot of damage to his generation. Therefore Klal Yisroel sticks to the rule that we don’t know who Moshiach is and as far as I know, in the famous seforim of Klal Yisroel, such as the Shulchan Aruch, and Rambam it doesn’t say anywhere that one has to have to believe that HIS Rebbe is Moshiach. The identity of the Moshiach as far as I know is hidden from people until the correct time will come B’miheira B’yameinu.
As a side point, and maybe this is where your friend is mistaken, there are Rishonim that when they would write the name of their Rebbe they would write MY master, may he live and be well. in Hebrew it would be מורי שיחיה. When that is written as an acronym, it is written משי”ח, but it is never meant to refer to his Rebbe as the Messiah himself!