God's promise to the Israelites presents a dual vision for their future homeland, combining strictly defined geographic borders with the potential for limitless expansion. The primary approach among commentators is that this vision contains two distinct directives [רמב״ן, הטור הארוך, מלבי״ם, רש״ר הירש, ביאור יש״ר, שטיינזלץ]. The first is a historical obligation to conquer the Land of Israel within its original boundaries, which includes uprooting the local nations and their idolatry. The second grants permission to capture additional territories far beyond the original borders, such as the lands of Shinar and Assyria. Any new territory acquired in this manner receives the exact same holy and legal status as the Land of Israel itself, meaning all commandments dependent on the land become fully applicable there.
However, this outward expansion comes with a strict condition. The right to conquer territories outside the designated land applies only after the conquest of the original borders is entirely complete [מלבי״ם, רש״ר הירש]. This is illustrated by King David's military campaigns in Syria and Aram. Because he initiated these foreign conquests before fully securing the homeland, specifically before Jerusalem was completely conquered, his acquisitions were classified as an individual conquest and did not attain the full holy status of the Land of Israel. There is a Talmudic dispute regarding this rule [רמב״ן]. While some maintain that an out-of-order conquest is legally invalid and leaves the new territory with the status of a foreign land, others argue that practical conquest alone fulfills God's promise, granting the area the full status of the Land of Israel.
On a basic historical level, the assurance of claiming newly walked territory refers directly to the generation entering the land and their battles against the seven Canaanite nations [רשב״ם, ביאור יש״ר]. The specific borders of this initial conquest are detailed by the commentators. The desert serves as the southern boundary [רשב״ם, ביאור יש״ר], though an alternative view identifies it as the eastern border [העמק דבר]. All agree that the Euphrates River marks the northern limit. The western boundary is identified as the Mediterranean Sea or the Western Ocean [רשב״ם, העמק דבר, אוהב גר, נתינה לגר]. In ancient times, directions were determined by facing east, which naturally placed this sea behind a person's back [רש״ר הירש]. The entire expanse stretches from the Israelites' location at that time in the southeast all the way to this western sea [רשב״ם].
The nature of these borders varied based on neighboring populations. The eastern and northern boundaries were strictly defined due to political constraints involving nations like Ammon and Moab, as well as specific groups designated for destruction, whereas the western and southern borders offered more flexibility for settlement expansion [העמק דבר]. Beyond the purely geographic layout, the boundary descriptions carry a deeper conceptual meaning. By drawing a linguistic connection between the final western sea and the end of days, the promise extends beyond a mere physical inheritance in this world, ultimately assuring a spiritual and eternal portion in the World to Come [השפתי כהן].