Definition and Context:
The phrase "a great nation" is a significant biblical concept primarily associated with God's promises to the patriarchs, particularly Abraham. It denotes not only a large population but also a people blessed by God, possessing land, and having a unique relationship with Him. This concept is foundational to the understanding of Israel's identity and destiny in the biblical narrative.

Biblical References:

1. Genesis 12:2 : The promise of a great nation is first introduced in God's call to Abram (later Abraham). God says, "I will make you into a great nation, and I will bless you; I will make your name great, so that you will be a blessing." This promise is part of the Abrahamic Covenant, which includes blessings, land, and a special relationship with God.

2. Genesis 18:18 : The reaffirmation of the promise is seen when God considers Abraham's role in His plans: "Abraham will surely become a great and powerful nation, and through him all the nations of the earth will be blessed." This highlights the universal scope of the promise, indicating that the greatness of the nation is not just for its own sake but for the blessing of all nations.

3. Genesis 46:3 : God reassures Jacob (Israel) as he prepares to go to Egypt: "I am God, the God of your father," He said. "Do not be afraid to go down to Egypt, for I will make you into a great nation there." This indicates that the formation of the great nation would continue even in foreign lands, emphasizing God's sovereignty and faithfulness.

4. Deuteronomy 4:6-8 : The greatness of the nation is also linked to its adherence to God's laws: "Observe them carefully, for this will show your wisdom and understanding in the sight of the peoples, who will hear of all these statutes and say, 'Surely this great nation is a wise and understanding people.' What other nation is so great as to have their gods near them the way the LORD our God is near us whenever we pray to Him?" Here, the greatness is associated with wisdom, understanding, and the presence of God.

5. 1 Kings 3:8-9 : Solomon, in his prayer for wisdom, acknowledges the vastness of the nation: "Your servant is here among the people You have chosen, a people too numerous to count or number. So give Your servant a discerning heart to govern Your people and to distinguish between right and wrong. For who is able to govern this great people of Yours?" This reflects the fulfillment of the promise in terms of population and the need for divine wisdom to lead such a nation.

Theological Significance:
The concept of a "great nation" is deeply intertwined with God's covenantal promises and His redemptive plan. It underscores God's initiative in choosing and blessing a people through whom He would reveal Himself to the world. The greatness of the nation is not merely in numbers or power but in its unique relationship with God, its role in His purposes, and its impact on the world. The promise of becoming a great nation is ultimately fulfilled in the broader narrative of salvation history, pointing to the coming of the Messiah and the inclusion of all nations in God's redemptive plan.