במדבר, פרק ל״ב, פסוק כ׳

When finalizing the agreement with the tribes of Gad and Reuben, Moses accepts their offer to join the military campaign in exchange for territory east of the Jordan River. However, his response is far more than a technical approval. He fundamentally transforms their perspective and the underlying motive for their participation. Moses establishes a double condition, which is a legal requirement to validate the agreement [תולדות יצחק]. Because performing a formal physical act of acquisition with such a massive group would take too much time, Moses turns their promise into a commitment to Heaven. A verbal promise to God functions as a practical acquisition and becomes immediately binding.

The primary approach among commentators focuses on a crucial shift in how the impending battles are defined. The tribes initially offered to march as the vanguard ahead of their fellow Israelites, driven by a sense of civic fairness, national brotherhood, and a desire to share the burden of conquest. Missing from their proposal was any mention of God, reflecting an absolute reliance on their own military strength. Moses corrects this worldview, demanding that they march into battle before God. He warns that fighting solely out of social obligation or personal interest is inadequate and can be considered a sinful lack of faith. The campaign must be a commanded war intended to fulfill God's will, sanctify His name, and defeat His enemies [אור החיים, הכתב והקבלה, ברכת אשר, אלשיך].

This distinction defines the very nature of the war. Marching ahead of the Israelites implies a natural conflict dependent on human strength. Marching before God signifies a miraculous campaign where God is the true warrior defeating the enemy. In this higher state, divine providence protects the soldiers because of their pure intentions [מלבי״ם]. Consequently, preparing for battle requires more than just physical weapons, as it demands spiritual fortification and the accumulation of merit [אור החיים].

Moses uses this divine focus to address the tribes' previously distorted priorities. They had requested to build enclosures for their livestock before constructing cities for their children, placing material wealth above human life. Moses signals that prioritizing property over people is fundamentally wrong. Yet, this backward order can only be tolerated if they fight before God. In a miraculous war supervised by God, He will naturally protect their families, making massive fortifications unnecessary and allowing them to tend to their livestock first. However, if they rely solely on their own military strength, leaving their children vulnerable while securing their wealth is a severe sin [מלבי״ם].

Finally, Moses emphasizes that participating in the war means seeing the mission through to absolute completion. Even if God miraculously removes the enemies, the land is not considered conquered until the Israelites physically capture the cities. The obligation of these tribes will only conclude when the entire land is fully secured. They cannot settle into a peaceful inheritance while their brothers are left to struggle with unconquered territories [רלב״ג].