Numbers 29:12-13

12“Five days later, on the fifteenth day of the same month, you must call another holy assembly of all the people, and you may do no ordinary work on that day. It is the beginning of the Festival of Shelters, a seven-day festival to the Lord.

13On the first day of the festival, you must present a burnt offering as a special gift, a pleasing aroma to the Lord. It will consist of thirteen young bulls, two rams, and fourteen one-year-old male lambs, all with no defects.