Deuteronomy 16:10-17

Then you shall keep the Feast of Weeks to the LORD your God with the tribute of a freewill offering from your hand, which you shall give as the LORD your God blesses you. You shall rejoice before the LORD your God, you and your son and your daughter, your male servant and your female servant, the Levite who is within your gates, the stranger and the fatherless and the widow who are among you, at the place where the LORD your God chooses to make His name abide. And you shall remember that you were a slave in Egypt, and you shall be careful to observe these statutes. “You shall observe the Feast of Tabernacles seven days, when you have gathered from your threshing floor and from your winepress. And you shall rejoice in your feast, you and your son and your daughter, your male servant and your female servant and the Levite, the stranger and the fatherless and the widow, who are within your gates. Seven days you shall keep a sacred feast to the LORD your God in the place which the LORD chooses, because the LORD your God will bless you in all your produce and in all the work of your hands, so that you surely rejoice. “Three times a year all your males shall appear before the LORD your God in the place which He chooses: at the Feast of Unleavened Bread, at the Feast of Weeks, and at the Feast of Tabernacles; and they shall not appear before the LORD empty-handed. Every man shall give as he is able, according to the blessing of the LORD your God which He has given you.