"And you took them on the first day" * - this is the fifteenth day and you say on the first day?

R. Yehoshua Daschnin in the name of R. Levi said: Parable to a state that owes taxes to the king and the king goes to collect it. Within ten miles the great men of the state went out and cursed him - he allowed them a third ... Within five miles, the country's middle class went out and cursed him - he allowed them another third. When he entered the country, all the people of the state went out, men and women and children and cursed him - and permitted them everything.

The king said to them: What was gone is gone. from now on we start the accounting. it is like on the eve of Rosh Hashana, the greatest of the generation is interested and God allows them one-third of their sins. From Rosh Hashana to Yom Kippur the individuals are interested and God allows them a third of their sins. And on the Day of Atonement, all of them, men, women and children are interested and God tells them, to Israel: what is gone is gone, from now on we shall start the accounting.

From Yom Kippur to the holiday, all of Israel is busy with mitzvot: this one with his sukkah and this one with the lulav. And on the first good day of the holiday of all Israel, they stand before the Holy One, blessed be He, and their lulavim and etrogs in their hands, and cast them into the name of the Creator. And God tells them: "What is gone is gone, from here we will begin to calculate." Therefore, Moses warns Israel, "And you shall take them on the first day."

*according to Leviticus, 23, 39-40: “So beginning with the fifteenth day of the seventh month, after you have gathered the crops of the land, celebrate the festival to the LORD for seven days; the first day is a day of sabbath rest, and the eighth day also is a day of sabbath rest. 40 On the first day you are to take branches from luxuriant trees—from palms, willows and other leafy trees—and rejoice before the LORD your God for seven days.”