Bible Notes Online - Numbers 18 - ESV
Commentary

v1-7: The people had become fearful of approaching God, 17.12-13; the priests' role in approaching God for the people was therefore of greater importance. The way to God was open, but the people had to come God's way, see 16.40. For the Christian, Jesus Christ is the way to God; we come in His Name.

v5: Unless they came the proper way, wrath would again fall on the people. Similarly, Christ has borne God's wrath for us, see Rom 5.9; Gal 3.13.

v8-19: The priests were fed from the offerings of the people.

v20: In contrast, the priests were to have no land in Canaan; their inheritance was the Lord God Himself.

v22: The Israelites could now not go near the Tabernacle, the Levites bearing that responsibility, as in v1-4..

v25-29: The Levites themselves had to give a tithe of all they received to Aaron, as their own offering to God.