We saw in last weeks Parsha how the wrath of G-d was kindled against the Jewish people for sinning with the Moabite women, and a great plague broke out killing 24,000 people. It was only through the zealousness of Pinchas that the wrath of G-d was quieted. We can learn from this two important lessons:
1) As the Zohar writes, there is no sin that arouses the wrath and zealousness of G-d like that of sexual transgression.
2) We can please G-d and give him great joy, when we, like Pinchas, arouse our own wrath and zealousness AGAINST these sins. Not against others specifically, but against our own mind's tendency to stray after unhealthy and sinful lusting.
In the same way that G-d is zealous in detesting and in punishing sexual transgression, we too must use this very characteristic of zealousness when dealing with these desires. We must arouse a zealousness in our hearts to abhor and revile the poisonous lusting of our hearts that pulls us away from G-d and arouses his wrath against us. In other words, instead of becoming aroused by something we may have seen for example, we need to learn to let our zealousness for G-d become aroused in our minds and hearts instead.
And one who indeed trains himself to arouse his zealousness in this regard, he will achieve true inner "peace". Like G-d said to Pinchas in this week's Parsha: "Pinchas the son of Elazar the son of Ahron the Priest has cooled my wrath from upon the Jewish people through his zealousness in their midst, and therefore I did not destroy the Jewish people in MY zealousness. Therefore I say, I give him my treaty of PEACE".