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 105: Impurity caused by Discharge
Leviticus 15:16 "When a man discharges..."

The impurity of Shichvat Zerah may befall a man.

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One who is full of himself fills all the space around him. There is no room left for anyone else. Therefore, he despises another person by virtue of the space that other person consumes. He may give reasons for his disdain, but the reasons are secondary.

This is called wanton hatred. It is the reason given for our exile. It is the core of all evil. It is balanced and cured by wanton acts of love and kindness.

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