Amar Rav Acha Yafa Sichoson 5739 The union of Yitzchok and Rivkah takes up so much space in Torah because it is the basis for all of Yiddishkeit: Yichud M”A and BA”N. By Yitzchok and Rivkah it is only spiritual, but by us it is (also) physical. Every Mitzvah really is a Yichud M”A and BA”N, but they are individual (detailed) unions, while the marriage of Yitzchok and Rivkah is the Yichud M”A and BA”N on the level of Klal and Klal Gadol. We can be Hashem’s Eved (slaves) to be vessels for this union. The Rebbe connects this to the Bittul of Rosh Hashana. This is achieved especially through Tefilla.
