יהושע, פרק ד׳, פסוק ד׳

Moments after the waters of the Jordan River split, a specific group of twelve men is tasked with lifting stones from the exposed riverbed. These representatives, one from each tribe, were chosen and organized by Joshua well before God commanded the gathering of the stones [מלבי״ם, אברבנאל, ביאור שטיינזלץ]. Originally, Joshua selected them for a different purpose: to stand close to the Ark of the Covenant. They were meant to serve as firsthand witnesses, observing and testifying how the river stopped flowing the exact moment the priests entered the water [מצודת דוד].

Once God gave the new instruction to build a stone monument, Joshua shifted the focus of these twelve witnesses, assigning them this additional responsibility [מלבי״ם, אברבנאל]. Relying on this pre-selected group solved an immediate problem. The rest of the Israelites were hesitant to linger in the dry riverbed. They were afraid that a sudden sin might cause the miracle to end, bringing the waters crashing back down upon them. Because of this widespread fear, Joshua did not ask the general public for new volunteers. Instead, he relied on the men he had already prepared. Having stood up close and witnessed the miracle from its very beginning, these twelve men were uniquely ready and confident to complete the task without fear [אלשיך].