26 "Speak thus to the Levites, and say to them: 'When you take from the children of Israel the tithes which I have given you from them as your inheritance, then you shall offer up a heave offering of it to the Lord, a tenth of the tithe. 27 And your heave offering shall be reckoned to you as though it were the grain of the threshing floor and as the fullness of the winepress. 28 Thus you shall also offer a heave offering to the Lord from all your tithes which you receive from the children of Israel, and you shall give the Lord's heave offering from it to Aaron the priest. 29 Of all your gifts you shall offer up every heave offering due to the Lord, from all the best of them, the consecrated part of them.'

Matthew Henry's Commentary on Numbers 18:26-29

Commentary on Numbers 18:20-32

(Read Numbers 18:20-32)

As Israel was a people not to be numbered among the nations, so Levi was a tribe to be distinguished from the rest. Those who have God for their Inheritance and their Portion for ever, ought to look with holy contempt and indifference upon the possessions of this world. The Levites were to give God his dues out of their tithes, as well as the Israelites out of their increase. See, in 2 Thessalonians 3:10. 2. We must be sure that God has his dues out of it. We have the comfort of our substance, when we have honoured the Lord with it. Ye shall bear no sin by reason of it, when ye have heaved the best from it. We should give alms of such things as we have, that all may be holy and comfortable to us.