The Rebbe and the Rogatchover on the definition of the mitzvah of binyan Bais Hamikdash, whether it’s about the ‘action of building’, or to ‘have a Mikdash built’, and its ramifications in the avodah of shmiras & bedikas hamikdash, the histalkus of the Rebbe Rashab and our tzipiyah to Moshiach.