The concept of “Ushpizin,” or, guests invited into our Succa, is based on a comment from the Zohar. This is explained clearly in “the Book of our Heritage,” also known as Sefer Hatoda’ah.
When the people of Israel leave their homes, and enter the Succa for the sake of Hashem’s Name, they achieve the merit of welcoming the Divine Presence. When this happens, all of the faithful shepherds descend from the Garden of Eden, and come to the Succa as their guests.
The seven guests are, Abraham, Isaac, Jacob, Joseph, Moshe, Aaron, and David. These seven dwell with all Israel in their Succot all seven days of the festival, except that each day one of them leads the others. Others place Moshe and Aharon in the order before Yosef.
Among Sephardic Jews, it is customary to prepare an ornate chair and cover it in fine cloth, and place holy books on it and declare, “This is the chair of the Ushpizin.” There is also the intention to reflect on the lives of these seven unique individuals. We can gain inspiration by noting how each was faced with great challenges that they needed to overcome. Because they succeeded, they are viewed as the “seven shepherds of Israel,” who led their flocks with great loyalty and love.
This is another feature of the holiday of Succot, that gives it, its special character of joy and happiness, that gives it one of its names, זמן שמחתינו, “the time of our joy.”