Introduction:
Psalm 81 is a significant chapter in the Book of Psalms, attributed to Asaph, a prominent Levite musician appointed by King David. This psalm is a communal hymn that calls the people of Israel to worship and obedience, reflecting on God's past deliverance and the consequences of disobedience. It is traditionally associated with the Feast of Tabernacles, a time of joyous celebration and remembrance of God's provision.

Structure and Themes:
Psalm 81 can be divided into three main sections: a call to worship (verses 1-5), a reminder of God's deliverance and commands (verses 6-10), and a lament over Israel's disobedience (verses 11-16).

1. Call to Worship (Verses 1-5):
The psalm begins with an exuberant call to worship: "Sing for joy to God our strength; make a joyful noise to the God of Jacob" (Psalm 81:1). The use of musical instruments such as the tambourine, harp, and lyre is encouraged, emphasizing the celebratory nature of the occasion. The reference to the new moon and full moon suggests the timing of the festival, likely the Feast of Tabernacles, which was a time of national gathering and worship.

2. Reminder of God's Deliverance and Commands (Verses 6-10):
In this section, God speaks directly to His people, reminding them of His mighty acts of deliverance. "I relieved his shoulder of the burden; his hands were freed from the basket" (Psalm 81:6) recalls the liberation from Egyptian slavery. God emphasizes His role as the one true God who delivered Israel and provided for their needs, urging them to listen and obey: "I am the LORD your God, who brought you up out of Egypt. Open wide your mouth, and I will fill it" (Psalm 81:10).

3. Lament Over Israel's Disobedience (Verses 11-16):
The tone shifts as God laments Israel's refusal to listen and follow His ways: "But My people would not listen to Me, and Israel would not obey Me" (Psalm 81:11). This disobedience led to God allowing them to follow their own stubborn hearts, resulting in missed blessings and protection. The psalm concludes with a poignant expression of what could have been if Israel had obeyed: "How quickly I would subdue their enemies and turn My hand against their foes" (Psalm 81:14).

Theological Significance:
Psalm 81 underscores the importance of worship, obedience, and remembrance of God's past faithfulness. It serves as a reminder of the covenant relationship between God and Israel, highlighting the blessings of obedience and the consequences of turning away. The psalm reflects God's desire for His people to trust in Him fully and experience the fullness of His provision and protection.

Liturgical Use:
Traditionally, Psalm 81 is associated with the Feast of Tabernacles, a time of thanksgiving and remembrance of God's provision during the wilderness wanderings. Its themes of deliverance and covenant faithfulness make it suitable for liturgical use during times of communal worship and reflection on God's past and present faithfulness.

Conclusion:
Psalm 81 remains a powerful call to worship and obedience, reminding believers of the importance of listening to God's voice and following His commands. Through its historical context and timeless message, it continues to inspire and challenge the faithful to live in accordance with God's will.