We are on the eve of Yom HaKippurim, when all of Am Israel do Teshuva and confess their sins, once a year. Since Teshuva is at the center of this day, we will discuss a point regarding it.
 

Masechet Yoma 86b brings Rabbi Yochanan's drasha which says that a man's Teshuva is so great that it supersedes a prohibition of the Torah:
 

Rabbi Yochanan says: Teshuva is so great that it displaces a Torah prohibition, as it says (Yirmiyahu 3:1): "Saying: lo, will a man send away his wife, and she will leave him and marry another man – can he (the first husband) go back to her again, shall not that land be defiled? But you were adulterous with many lovers and (nevertheless) return to Me, says HaShem."
 

Rashi explains that the Torah prohibition which is mentioned is "Her first husband who sent her away will not be permitted to take her again, etc." That is: the relationship between Israel and HaShem is like that between a husband and a wife, and if the husband divorces the wife and she marries someone else (who afterwards also divorces her or dies) – the first husband is forbidden to marry her again. But Teshuva has the power to nullify this "prohibition."
 

In his book Tosefet Yom HaKippurim, the Maharam Ben Haviv asks: what is the chiddush that Teshuva supersedes a prohibition? Isn't it a general principle that aseh (a positive command) displaces lo ta'aseh (a negative command)? What is special about Teshuva in comparison to all the other positive commands in the Torah?
 

Indeed, according to the Rambam, Teshuva itself is not a Mitzvah, but Vidui (confession) is, and Teshuva itself is the path a man chooses to follow in order to attain atonement (see Minchat Chinuch Mitzvah 364). This can be resolved as follows: in spite of the fact that Teshuva is not a positive command, it has the power to nullify the prohibition of "Her first husband will not be permitted." This is the greatness and the power of Teshuva.

However, for the other Rishonim who hold that Teshuva is a positive command, the question still demands an answer.
 

We heard an appropriate principle from HaRav Moshe Dimentman ztz"l which resolves this question (and the Tosefet Yom HaKippurim mentions this among his other answers):
 

It is brought in Masechet Eruvin p. 100a, that if the blood of an olah sacrifice and the blood of a bechor became mixed together, now the Cohen is in quandary: the blood of the bechor has to be given in two (which are four) matanot - placements of blood, and the blood of the olah is given in only one matanah.
 

If the Cohen will give only one matanah, as a result he will detract from the giving of blood of the bechor, and if he will give two placements of the mixed blood, it will turn out that he is adding to the giving of the blood of the olah.
 

Rabbi Eliezer and Rabbi Yehoshua disputed on this point. According to Rabbi Eliezer, four matanot should be given so as not to transgress the prohibition of bal tigra (do not detract). In contrast, Rabbi Yehoshua reasons that only one placement of blood should be given, and this is in order to not transgress bal tosif (do not add). Rabbi Yehoshua's rationale is that it is preferable to passively transgress bal tigra, detracting, than to actively transgress bal tosif, adding. And the Halacha is according to Rabbi Yehoshua (see Rambam, Pesulei HaMekudeshin 2:11).
 

The Tosefot raise a question regarding this:

Why do we not implement the principle of aseh diplaces lo ta'aseh, and instruct the Cohen to give four, and on the strength of the aseh of giving the blood of the bechor, the prohibition of bal tosif (in giving more blood of the olah than the Torah prescribes) will be displaced, and ostensibly Rabbi Eliezer is correct!

The Tosefot answer this question and present an important principle: an aseh does not displace a lo ta'aseh when the aseh came through transgression. The Cohen transgressed by being careless, and through negligence the bloods mingled, and now he doesn't have the privilege to invoke the clause "aseh displaces lo ta'aseh" in order to remedy the damage done.
 

We can bring support for this principle from another example. Masechet Sanhedrin 113a says regarding ir hanidachat (a condemned city):
 

Any city which has even one Mezuzah – does not become ir nidachat, as is written: "And you shall burn the city with fire and all its spoils, entirely" and where there is a Mezuzah – this is impossible, as is written: "You shall not do thus to HaShem your Lord."
 

The Torat Chaim (Sanhedrin 71a) asks: Why does the positive command "You shall smite the dwellers of the city, and you shall gather all its spoil and burn it with fire" not supersede the prohibition of "You shall not do thus to HaShem your Lord"?
 

In other words, why does the aseh "and burn it with fire" not displace the lo ta'aseh "you shall not do etc."?
 

According to the abovementioned principle, this can be understood. The command "and burn it with fire" is created through sin. It comes in order to eradicate the infamy of ir hanidachat. It does not have the power to supersede the prohibition of "You shall not do thus" since it was conceived and born in the grievous sin of the dwellers of the city.

Through this we can learn about the great power of Teshuva. Teshuva has the power to nullify the prohibition "Her first husband will not be permitted, etc." even though we got to the current situation through our sin and our distancing from HaShem. And this is the greatness of Teshuva which brings Israel close to their Father in Heaven – "To unite the wife of youth to her beloved in love, brotherhood and friendship."
 

Even though "we transgressed and rebelled" – "You did forgive" and continue to forgive Your nation Israel, since "You are sons to HaShem your Lord." 
 

Wishing all of Am Israel g'mar chatima tova and complete Teshuva.

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