שמות, פרק מ׳, פסוק ל״א

Setting up the Tabernacle required careful preparation, focusing heavily on the purity of those serving in the sacred space. Washing the hands and feet was an absolute requirement before anyone could approach the holy area or offer sacrifices. This action was not a full body immersion, but a specific cleansing of the extremities [ביאור שטיינזלץ]. Rather than being a new instruction, this describes an ongoing practice and the ultimate purpose of the washbasin itself [קאסוטו]. It reflects how the priests consistently prepared themselves for service [תורה תמימה].

The purification had to come directly from the washbasin, perhaps using a special cup to pour the water [פרדס יוסף]. The water could not be taken from any other sacred vessel. For someone like Moses, who maintained a high and unwavering spiritual focus, this initial purification from the basin was all that was needed [צפנת פענח]. Although an earlier cleansing was already recorded, that initial washing was either done using an ordinary vessel before the Tabernacle items were officially sanctified, or the current account simply confirms that the previous divine command was now being fulfilled [מלבי״ם].

The inclusion of Moses washing alongside Aaron and his sons is unusual and draws significant attention. The primary approach among commentators is that during the inauguration period, Moses functioned as a full priest and was therefore obligated to wash before serving. On the eighth day of the inauguration, Moses and Aaron's family were equal in their priestly status, making this the only instance where someone who was not a permanent priest washed from the basin [רש״י, ביאור יש״ר].

However, there is some debate about whether Moses actually served as a priest on that specific eighth day [ריב״א]. If he did not offer sacrifices, his washing was necessary simply to gain entry into the Tent of Meeting, even without performing any official duties [העמק דבר]. Another perspective suggests that during the first seven days of the inauguration, the Tabernacle functioned as a temporary altar where washing the hands and feet was not required, making this the first time Moses was obligated to do so [צפנת פענח].

Beyond the historical events, grouping Moses, Aaron, and his sons together establishes a practical rule regarding the size of the washbasin. It must hold enough water to purify four priests at the exact same time. The text groups them together to teach the necessary capacity of the vessel, regardless of whether all four men actually performed the priestly service at that very moment [תורה תמימה].