What did God give the Levites as their inheritance in return for their service at the Tent of Meeting?

Answer: All the tithes in Israel

Numbers 18:21: "I have given to the Levites all the tithes in Israel as an inheritance in return for the work they do."

“Behold, I have given to the Levites all the tithes in Israel as an inheritance in return for the work they do, the service of the Tent of Meeting.”— Numbers 18:21 (BSB)