במדבר, פרק ב׳, פסוק ט״ז

The organization of the Israelite camps in the desert involved not only where the people pitched their tents, but also the precise order in which they marched. Within this structured arrangement, the total count of the men belonging to the camp of Reuben reaches one hundred and fifty-one thousand, four hundred and fifty.

When the time comes to break camp and move forward on the journey, this large group follows a strict sequence. The camp of Reuben is assigned the second position in the overall marching order, stepping out onto the path immediately after the banner of the camp of Judah [ביאור שטיינזלץ].