Matthew Henry on Exodus 30:17-21

A large vessel of brass, holding water, was to be set near the door of the tabernacle. Aaron and his sons must wash their hands and feet at this laver, every time they went in to minister. This was to teach them purity in all their services, and to dread the pollution of sin. They must not only wash and be made clean, when first made priests, but must wash and be kept clean, whenever they went to minister. It teaches us daily to attend upon God, daily to renew our repentance for sin, and our looking to the blood of Christ for remission; for in many things we daily offend.