Im Bichkosai 5745.
The Rebbe calls this Ma'amar of the Mitteler Rebbe a 'wondrous Ma'amar', It explains three levels in each and every Mitzvah: 1) Commandment (as the Soul is contained in the Nefesh HaBahamis; B'Chol Livuv'cha), 2) A promise that you'll do it [as the Soul is by itself], 3) A story- the Mitzva (litterally) does itself (On the level of teh Yechida where Mitzvos 'do' themselves. 'Bchol MiOdecah'). He connects this to Shma... Echad and Boruch Sheim and then to the Mitzva of viAhavta. It is tied in to Bichukosai, that has three points in the first Podsuk: 10 being aMiHalech, and the level of chakika, 20 Guarding the Ohtr Makif retrieved through Birurim, 3) Creating keilim for this higher Ohr.