Rashi on Emor | Festivals and Fields

We discuss Rashi on Parashat Emor.  One of Rashi’s comments touches upon the question of where our focus must be - on the Beit HaMikdash or on the foundation of a good society? In the midst of Parshat haMoadim (the section about the agricultural festivals), a law about reaping fields reappears. Pe'ah is an agricultural mitzva, and helping the poor is important, but what is this mitzva doing here? What accounts for the repetition after it appears in Parashat Kedoshim? What is the significance of its placement in the midst of the regalim (Pilgrimage Festivals)?