Verses 17-21 (Exodus 30:17-21)

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, Exod. 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. They then had a laver for the priests only to wash in, but to us now there is a fountain open for Judah and Jerusalem to wash in (Zech. 13:1), an inexhaustible fountain of living water, so that it is our own fault if we remain in our pollution. 2. For the using of this laver. Aaron and his sons must wash their hands and feet at this laver every time they went in to minister, every morning, at least, Exod. 30:19-21. For this purpose clean water was put into the laver fresh every day. Though they washed themselves ever so clean at their own houses, that would not serve; they must wash at the laver, because that was appointed for washing, 2 Kgs. 5:12-14. This was designed, (1.) To teach them purity in all their ministrations, and to possess them with a reverence of God?s holiness and a dread of the pollutions of sin. They must not only wash and be made clean when they were first consecrated, but they must wash and be kept clean whenever they went in to minister. He only shall stand in God?s holy place that has clean hands and a pure heart, Ps. 24:3, 4. And, (2.) It was to teach us, who are daily to attend upon God, daily to renew our repentance for sin and our believing application of the blood of Christ to our souls for remission; for in many things we daily offend and contract pollution, John 13:8, 10; Jas. 3:2. This is the preparation we are to make for solemn ordinances. Cleanse your hands and purify your hearts, and then draw nigh to God, Jas. 4:8. To this law David alludes in Ps. 26:6; I will wash my hands in innocency, so will I compass thine altar, O Lord.

- Matthew Henry's Complete Commentary