Adam Clarke on Deuteronomy 12:19

Forsake not the Levite - These had no inheritance, and were to live by the sanctuary: if therefore the offerings were withheld by which the Levites were supported, they of course must perish. Those who have devoted themselves to the service of God in ministering to the salvation of the souls of men, should certainly be furnished at least with all the necessaries of life. Those who withhold this from them sin against their own mercies, and that ordinance of God by which a ministry is established for the salvation of souls.