This is not an error of duplication. The full-fledged version of this Mitzvah are many and change for those who are learning the one/three chapter a day. The Message for the day from "Bringing Heaven Down to Earth" at the end of this Mitzvah is different than that of yesterday.

Positive Mitzvah 127: The First Tithe
Numbers 18:24 "But the tithes of the Children of Israel which they offer as a gift"

We are commanded to give a tenth of all the land's produce to the Levites.

The Levites were not given an inheritance of land as were the other tribes.

Instead, this share of our crop is considered their inheritance.

Since there are other types of "tithes," (which means: a tenth of the amount), this one is called: "The First Tithe."

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People think that G-d first made a world and then gave us instructions to follow, so we won't mess it up. The truth is, the instructions came first, and the world was designed as the venue to carry them out. Therefore, to say that anything in the world could be an opposition to carrying out its Creator's will is an absurdity. There can be no opponents to the purpose of creation -- only meaningful challenges.

From: Bringing Heaven Down to Earth by Tzvi Freeman - tzvif@aol.com