Matthew Poole and continuators on Exodus 29:4

4 And Aaron and his sons thou shalt bring unto the door of the tabernacle of the congregation, and shalt wash them with water .

Taken out of that laver, Exod. 30. 18. This signified the universal pollution of all men, and the absolute need they have of washing, especially when they are to draw nigh to God. And this outward washing was onely typical of their spiritual washing by the blood and spirit of Christ in order to their acceptance with God.