Numbers 18:11-12

11Also, you will receive part of the special gifts that the Israelites lift up in front of me. I have given it to you and to your sons and daughters, for all time. Every person who lives in your house may eat it. But they must be clean at the time.

12I will give to you the best olive oil, the best wine and the best grain. The people give to the Lord the first part of these that they get.