Rambam - Sefer HaMitzvos: Positive Mitzvah 109: Positive Mitzvah 109

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 109: Immersing in a Mikveh
Leviticus 15:16 "He shall bathe all his body in water"

Just as the Torah defines the different types of impurity - it also outlines the process for purification.

The Torah describes the purification process, commanding the impure person to immerse himself in a mikveh.

A mikveh is a special pool of water of a specific size.

Its water must come from a natural source, rain or a spring.

In the beginning of the universe, the entire creation emerged from water. After an impure person dips in the mikveh, he rises up as a new creation; purified and prepared to serve HaShem.

Never underestimate the power of a simple, pure deed done from the heart. The world is not changed by men who move mountains, nor by those who lead the revolutions, nor by those whose purse strings tie up the world. Dictators are deposed, oppression is dissolved, entire nations are transformed by a few precious acts of beauty performed by a handful of unknown soldiers.
In fact, it was Maimonides who wrote in his code of law, "Each person must see himself as though the entire world were held in balance and any deed he might do could tip the scales."

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