The Torah associates the three pilgrim festivals with two distinct concepts. First, the Torah relates them to the Exodus from Egypt. The Torah also associates the pilgrim festivals with the natural aspect of Eretz Yisrael, its agricultural cycles.
Not a word about any historical memory of the Exodus and the giving of the Torah is mentioned in relation to the “Festival of the Ingathering” (Sukkot) in Shemot. However, the section on the festivals in Sefer Vayikra clarifies that Sukkot is celebrated in the seventh month, joining it to the Festival of the Ingathering.
In our discussion, as we relate to the offerings listed in Bemidbar, we argue that the “Festival of Sukkot” and the “Festival of the Ingathering” are in fact two festivals on the same date - two distinct festivals that occur simultaneously. In Devarim, they two aspects are explicitly linked to convey an important message counteracting the dangers of excessive pride at the agricultural abundance.
Though the pilgrimage commemorations and the "stay-at-home" celebrations each focused on a different aspect, eventually, the ideal of Devarim was realized and the nation was more united in its celebrations of both holidays together.
