במדבר, פרק ל״ב, פסוק כ״ח

Securing territory outside the original borders of the Promised Land requires a binding, long-term commitment. Since Moses will not cross the Jordan River and this agreement will only be fulfilled years after his death, he must entrust its execution to the future leadership of the nation, namely Eleazar, Joshua, and the heads of the tribes [ביאור שטיינזלץ].

Moses does not simply issue a direct order to the tribes of Gad and Reuben. Instead, he officially appoints the future leaders and grants them authority over these tribes to enforce the specific conditions of their agreement [רש"י, שפתי חכמים, מזרחי, גור אריה, ברכת אשר על התורה]. He gives the new leadership a clear, uncompromising directive: they must not grant these tribes their requested land immediately. The tribes will only receive their territory after they march alongside the rest of the nation and participate in the conquest of the land [ספורנו].

To ensure compliance, Moses establishes a precise legal framework known as a double condition. He dictates that if the tribes keep their promise and cross the Jordan River as the vanguard, they will earn the land of Gilead as their inheritance. However, if they break this condition, they will forfeit their right to the territory east of the Jordan and will be forced to receive their land through a lottery within the land of Canaan, just like the rest of the Israelites [רלב"ג, מלבי"ם].

The exact scope of their military obligation is also clearly defined. Because they committed to go to war before God, implying a battle accompanied by divine providence and miracles, Moses grants them a specific concession. He allows them to return to their families and their new land immediately after the military conquest ends. They are exempt from waiting in the land of Israel throughout the lengthy process of dividing the territories among the other tribes [מלבי"ם].