I am reading a Devar Torah by an esteemed Rosh Yeshiva which says "Furthermore, the Midrash explains that when we lift our lulavim and esrogim on Sukkos, it is essentially a celebration of life. The Midrash illustrates this with an analogy: After a king judges his subjects, and grants them an additional year of life, they display royal banners in honor of the king, in a demonstration of their gratitude for his judgment. Likewise, the Midrash explains, we presume that Hashem awarded us another year of life on Yom Kippur, and in gratitude for that, we display His royal “flag” – the Four Species – on Sukkos."
Anyone know where this Medresh is? It's certainly not the one in Vayikra Rabbah 30:2.