Moses
Numbers 18:26ESV·traditional attribution

“Moreover, you shall speak and say to the Levites, ‘When you take from the people of Israel the tithe that I have given you from them for your inheritance, then you shall present a contribution from it to the LORD, a tithe of the tithe.

Matthew Henry Presbyterian @wholebiblehenry

Here is a further account of the provision that was made both for the Levites and for the priests, out of the country. I. They must have no inheritance in the land; only cities to dwell in were afterwards allowed them, but no ground to occupy: Thou shalt not have any part among them, Num 18:20.

Commenting on Numbers 18:20-32

John Gill Reformed Baptist @doctorgill

And this your heave offering,.... The tithe of the tithe, which though not properly heaved or lifted up, as the heave offerings, strictly so called, were, any more than the tithe itself, Num 18:24; yet is so called, because separated to the use and service of the Lord, as they were: shall be reckoned unto you, as though it were the corn of the threshingfloor...

Jamieson-Fausset-Brown Reformed @jfbcommentary

THE LEVITES' PORTION. (Num 18:21-32) I have given the children of Levi all the tenth in Israel for an inheritance, for their service which they serve--Neither the priests nor the Levites were to possess any allotments of land but to depend entirely upon Him who liberally provided for them out of His own portion; and this law was subservient to many important purposes--such as that...

Commenting on Numbers 18:21-32