Numbers 18:27

And this your heave offering shall be reckoned unto you, as though it were the corn of the threshingfloor, and as the fulness of the winepress.

Cross-reference

Numbers 18:30 restates the same principle: the Levites' heave offering counted as produce, echoing 18:27.

Numbers 15:20 uses the same 'threshing floor' imagery for firstfruits of dough, paralleling how the Levites' tithe is credited as produce.

Ezekiel 44:30 describes priests receiving firstfruits and contributions, echoing the Levites' system of tithes and contributions.