“Evaluate the loss of a mitzvah as opposed to its reward, and the reward of a sin as opposed to its deficit.”
Rebbi Chaim HaKohen asks: What is “the reward of a sin”? He cites the gemara in Kiddushin (39b) which states that if one abstains from doing an aveiroh he earns reward as if he had performed a mitzvah.
In light of this gemara, a person might contemplate the advantage of transgressing a sin and then desist from transgressing again, and in that way he will merit reward. Therefore, the Tanna admonishes one to bear in mind the danger involved in such activity because there is a possibility that one will not be able to prevail.
