The cycle of the festivals, the “appointed times” (in biblical parlance), denotes the movement of the Children of Israel from scarcity to abundance and from divinity to partnership to mortality. The covenantal meeting in a sacred time and place is intimately bound up with the abundance being distributed.
That the appointed times are sacred merely signifies that these are the moments when the covenantal partners get to meet to demark the meaning of the day. The sanctity is necessary because the covenantal partner had removed Himself from the ordinary life of the people. Prior to the sequestration of God's substance into the Tent of Appointment (Ohel Mo’ed) His presence was everywhere in the camp and the entire people were sacred because the entire people were in direct and immediate contact with their covenantal partner. After the sequestration, the sanctity is reserved only for appointed times and at the appointed tent when and where the encounter between the covenantal partners takes place.
The annual cycle begins with the paschal offering. Pesach offerings set apart the people from the divine by having them eat meat without offering it on an altar and without sharing it as an appeasing fragrance for God . Chag haMatzot has the people eating mortal food in the same (unleavened) form as God partakes of it. The last day of the chag stops the condition of independent divinity for the people, which is why Scripture calls the seventh day of chag haMatzot “atzeret”, the stop. These two festivals – chag pesach and chag haMatzot – situate the people outside of the Land of Israel.
Chag haShavuot brings the people into the land by displaying the first fruits and wheat before God through His priests, and by repeating the original declaration that first Israelite generation made when they took possession of the land, saying this land is the promised land which fulfills God's sworn obligation to the people. It is not clear that the entire people celebrated the festival at the same time, nor is it clear the urban class participated in the ceremony of the first fruits at all. The heave offering displays both mortal and divine food, doubletons (the sign of abundance) waved together as a symbol of covenantal fulfillment.
Chag haSuccot is about the divine food that begins in abundance and concludes in symbolic scarcity, with the Shemini Atzeret closing off the divine mimicking the mortal.