Deuteronomy 16:10-13

10Then you are to celebrate the Festival of Weeks before the Lord your God with the voluntary offering that you will bring, in proportion to how he has blessed you.

11You shall rejoice before him – you, your son, your daughter, your male and female slaves, the Levites in your villages, the resident foreigners, the orphans, and the widows among you – in the place where the Lord chooses to locate his name.

12Furthermore, remember that you were a slave in Egypt, and so be careful to observe these statutes.

13You must celebrate the Festival of Temporary Shelters for seven days, at the time of the grain and grape harvest.