Deuteronomy 26:11
And thou shalt rejoice in every good thing which the LORD thy God hath given unto thee, and unto thine house, thou, and the Levite, and the stranger that is among you. And thou shalt rejoice in every good thing which the LORD thy God hath given unto thee, and unto thine house, thou, and the Levite, and the stranger that is among you.
The command is to rejoice in every good thing the Lord gives to the individual and to the household. That rejoicing belongs to worship and to public acknowledgment of God's goodness when bringing the firstfruits offering to the sanctuary. The offering recognizes His goodness in delivering Israel from slavery in Egypt and giving them a land to dwell in, with the land itself and its harvest as gifts from Him. It recognizes Him as the true owner and the people as stewards of what He had provided.
The joy is not private but is to be shared with the household, the Levite, the stranger among them, and the poor through a hospitable welcome. Remembering and providing for the Levite, the stranger, the fatherless, and the widow so they can eat and be filled was a standing and continuing requirement under the tithing directions. The grateful offerings acknowledged God's goodness and provision.
The annual feasts, including the Feast of Tabernacles, gave occasions for this communal rejoicing, outdoor recreation, and social fellowship. The rejoicing includes thanking and praising God for temporal blessings, comforts, and gifts of His providence. It also includes giving glory to Him for the treasures of His grace.
Gratitude is to be taught to children at home by parental example and instruction. When children are taught to be grateful to the Giver of all good things, gratitude brings cheerfulness into family life. It encourages respect and reverence at school and church, and leads to reverent worship and grateful praise for God's gifts.