Deuteronomy 16:15
Seven days shalt thou keep a solemn feast unto the LORD thy God in the place which the LORD shall choose: because the LORD thy God shall bless thee in all thine increase, and in all the works of thine hands, therefore thou shalt surely rejoice.
The verse describes the seven-day Feast of Tabernacles, the closing harvest feast and crowning festal gathering of the year, held after gathering in corn and wine, including orchard fruit, oil, and wine. It was to be kept as a solemn feast unto the Lord in the place He would choose, as a yearly gathering. The appointed seasons were times to remember God's blessings, and the feasts provided appointed times for worship and social fellowship. Although fathers and sons were required to attend, the whole household often came.
The feast commemorated the years the Hebrews lived in tents during the wilderness journey, when the people left their houses for a week to live in leafy booths made from green branches, including pine or myrtle. Those booths were set up on rooftops, in streets, or outside the city in valleys and on hillsides. It came after the harvest when the people were free from labors and could devote themselves to its sacred joy. This followed the Day of Atonement when assurance that sins would be remembered no more left them at peace with God, and its observance resumed after the return from captivity.
The reason for rejoicing is that the Lord had blessed all increase and all the works of the hands, having watched over the people and blessed their work and harvest, including fruit produced by sun and rain, therefore they should surely rejoice. Its observance set aside ordinary and unnecessary work to remember God's blessings, combining joy and rejoicing with the solemnities of a holy sacred convocation in shared worship and social fellowship. The people were to bring offerings, first-fruits, tributes of thanksgiving, tithes into the treasury, and gifts and thank-offerings from orchard and field in proportion to what they had received. Thereby they acknowledged the Lord as the giver of all blessings and every earthly blessing as from Him.
The many sacrifices and profusion of blood shed with this harvest thanksgiving taught that even the bounties of the earth could come only through the cross of Calvary. The joy was to be shared by the whole community with hospitality, including servants, strangers, orphans, widows, Levites, and the poor. God covenanted and promised to bless the people in their increase and their work if they faithfully observed His requirements. Israel in this is an ensample to imitate in faithfulness and to shun in sin, and the feast is a pattern for yearly convocation meetings that all who possibly can attend are under obligation to attend, so that neglect to improve its light and blessings brings responsibility before God.