with which Aaron and his sons shall wash their hands and their feet.
Orders are here given, 1. For the making of a laver, or font, of brass, a large vessel, that would contain a good quantity of water, which was to be set near the door of the tabernacle, Exo 30:18. The foot of brass, it is supposed, was so contrived as to receive the water, which was let into it out of the laver by spouts or cocks.
Commenting on Exodus 30:17-21
For Aaron and his sons shall wash their hands and their feet thereat. Not in it, but at it; the laver had mouths or spouts, as Ben Melech says, from whence the water flowed when the priests washed their hands and feet at it; and so Bartenora says (z) they did not wash out of the laver, but from water flowing out of it; it...
For Aaron and his sons shall wash their hands and their feet thereat: (k) Signifying that he that comes to God must be washed from all sin and corruption.