Definition and Usage:
The term "All Israel" is a collective designation used throughout the Bible to refer to the entire nation of Israel, encompassing all twelve tribes. It signifies the unity and collective identity of the Israelites as God's chosen people. The phrase is employed in various contexts, including religious, political, and social settings, to emphasize the unity and shared heritage of the Israelites.

Biblical References:

1. Covenantal Identity:
"All Israel" is often used to highlight the covenantal relationship between God and the Israelites. In Deuteronomy 29:10-12 , Moses addresses "all Israel" as they stand before the Lord to enter into a covenant: "All of you are standing today before the LORD your God... so that you may enter into the covenant of the LORD your God and into the oath He is making with you today."

2. National Unity:
The term underscores the unity of the tribes, especially during significant national events. In 1 Samuel 7:5 , Samuel calls "all Israel" to Mizpah for a time of repentance and renewal: "Then Samuel said, 'Gather all Israel to Mizpah, and I will pray to the LORD on your behalf.'"

3. Political and Military Contexts:
"All Israel" is used in contexts of political and military mobilization. In 2 Samuel 5:1-3 , "all the tribes of Israel" come to David at Hebron to acknowledge him as king: "Then all the tribes of Israel came to David at Hebron and said, 'Here we are, your own flesh and blood.'"

4. Religious Observance:
The phrase is also used in religious contexts, such as the observance of Passover. In 2 Chronicles 35:1 , King Josiah keeps the Passover for "all Israel": "Josiah kept a Passover to the LORD in Jerusalem, and they slaughtered the Passover lamb on the fourteenth day of the first month."

5. Prophetic and Eschatological Significance:
In prophetic literature, "All Israel" can refer to the future restoration and salvation of the nation. Romans 11:26 speaks of a time when "all Israel will be saved," indicating a future fulfillment of God's promises to His people: "And so all Israel will be saved, as it is written: 'The Deliverer will come from Zion, He will remove godlessness from Jacob.'"

Historical Context:
The concept of "All Israel" is rooted in the historical formation of the Israelite nation, beginning with the patriarchs Abraham, Isaac, and Jacob, whose twelve sons became the progenitors of the twelve tribes. The unity of "All Israel" was first realized during the Exodus from Egypt and the subsequent conquest of Canaan under Joshua. Despite periods of division, such as the split into the northern kingdom of Israel and the southern kingdom of Judah, the ideal of a united "All Israel" persisted in the religious and cultural consciousness of the Jewish people.

Theological Implications:
Theologically, "All Israel" represents the collective identity of God's covenant people, called to live in obedience to His laws and to be a light to the nations. It underscores the themes of unity, faithfulness, and divine election. The concept also points to the eschatological hope of a restored and redeemed Israel, as prophesied in the Old and New Testaments.

Conclusion:
The term "All Israel" serves as a powerful reminder of the unity and shared destiny of the Israelites as God's chosen people. It encapsulates the historical, religious, and prophetic dimensions of Israel's identity and mission in the biblical narrative.