Likutei Sichos, vol 32, Emor 2, Rabbi Chaim Wolosow
https://www.torahrecordings.com/likutei-sichos/032/012_002 Likutei Sichos vol. 32 - Emor 2 - From Barley to Wheat: The Journey of Avodas Hashem The Rebbe explains why a Mincha before the Omer is invalid, but before the Shtei Halechem is valid after the fact. Through the Omer of barley and the Shtei Halechem of wheat, the Sicha maps the growth from self-discipline and refining the animal soul to joyful, elevated service of Hashem.