במדבר, פרק ז׳, פסוק ח׳

The distribution of transport equipment among the Levite families was carefully planned to match the physical weight and the sacred nature of their specific duties in moving the Tabernacle. The family of Merari was assigned four wagons and eight oxen. This large allocation was necessary because they bore the heaviest physical burden. Their responsibility was to transport the heavy structural framework of the Tabernacle, which included the boards, bars, sockets, pillars, pegs, and cords [חזקוני, ביאור שטיינזלץ]. All of this logistical work, encompassing the transport duties of both the Merari and Gershon families, operated under the direct supervision of Ithamar, the son of Aaron the priest.

In sharp contrast, the family of Kohath received no wagons at all. This absence was highly intentional. Their responsibility involved the most sacred items, such as the Ark of the Covenant and the holy vessels. Because of the supreme holiness of these objects, they could not be placed on carts. Instead, they had to be carried exclusively on the shoulders of the Levites. This distinction establishes a clear Commandment regarding how the holy vessels must be transported.

The strict importance of carrying the sacred items on the shoulder became starkly apparent generations later. King David initially made a grave error by placing the Ark of God on a new wagon rather than having it carried on the shoulder. This mistake resulted in the tragic death of Uzzah. Following that event, David recognized his oversight, corrected the procedure, and ordered the Levites to carry the Ark on their shoulders, perfectly honoring the original instructions God gave in the desert [רלב״ג].