Numbers 18:26

26 Thou shalt also speak to the Levites, and shalt say to them, If ye take the tithe from the children of Israel, which I have given you from them for an inheritance, then shall ye separate from it a heave-offering to the Lord, a tenth of the tenth.

Numbers 18:26 Meaning and Commentary

Numbers 18:26

Thus speak unto the Levites, and say unto them
Aaron was to tell them what a provision would be made for them on account of their service, but Moses was to inform them what part Aaron was to have out of it:

when ye take of the children of Israel the tithes which I have given
you from them for your inheritance;
which was done at the time of their harvest, and of the ingathering of the fruits of the earth:

then ye shall offer up an heave offering of it for the Lord;
in token of gratitude for the liberal provision he had made for the maintenance of them:

[even] a tenth [part] of the tithe;
a tenth part out of the tenth of the produce of the land of Israel.

Numbers 18:26 In-Context

24 Because I have given as a distinct portion to the Levites for an inheritance the tithes of the children of Israel, whatsoever they shall offer to the Lord; therefore I said to them, In the midst of the children of Israel they shall have no inheritance.
25 And the Lord spoke to Moses, saying,
26 Thou shalt also speak to the Levites, and shalt say to them, If ye take the tithe from the children of Israel, which I have given you from them for an inheritance, then shall ye separate from it a heave-offering to the Lord, a tenth of the tenth.
27 And your heave-offerings shall be reckoned to you as corn from the floor, and an offering from the wine-press.
28 So shall ye also separate them from all the offerings of the Lord out of all your tithes, whatsoever ye shall receive from the children of Israel; and ye shall give of them an offering to the Lord to Aaron the priest.

The Brenton translation of the Septuagint is in the public domain.