Yosef Karo

“ The last day of Yom Tov is called "Simchat Torah" because we rejoice on it, making a festive meal in honor of the finishing of the Torah. It is customary for the person who finishes the Torah and the one who starts Genesis to make a donation and invite everybody to party (Tur) . It is customary in these countries to take all of the Torahs out of the Ark on Simchat Torah at night and in the morning and to sing songs and praises. Every place should follow its customs. It is also the custom to circle the synagogue's Bimah with the Torah scrolls just like we circle with the lulav. ”