Mesillas Yesharim (end of chapter 4) explains the system of teshuva in a rational way, that through regretting one’s actions now, he undoes the desire for what he did in the past. Mesillas Yesharim compares this form of regret to the regret that plays a halachic role in annulling vows: “He who is repenting recognizes his sins and admits it, and reflects upon his evil and repents, and wishes that the sin had never been committed, as he would wish that a certain vow had never been made, in which case there is complete regret, and he desires and yearns that the deed had never been done, and suffers great anguish in his heart because it has already been done, and departs from it for the future, and flees from it — then the uprooting of the act from his will is accredited to him as the uprooting of a vow, and he gains atonement, as it states (Yishaya 6:7): “Your wrong will depart, and your sin will be forgiven.” The wrong actually departs from existence and is uprooted because of his suffering from and regretting now what took place in the past.”

The Ramchal is being mechadeish a source for the concept of teshuva within the laws of the Torah — namely, that of hataras nedarim [annulment of vows]. However, the Ramchal goes on to say that even though the chessed of teshuva does not go against Hashem’s trait of judgment and is not an out-and-out contradiction to Torah logic, teshuva is nevertheless not “the letter of the law.” In other words, it is obvious that on our own, we could never arrive at such a concept of teshuva, as the Medrash states (similar to what was quoted above from Makkos Yerushalmi, that “the Torah was asked, what should be the punishment of the sinner? Torah replied: ‘Let him bring a korban asham [guilt offering] and gain atonement.” Meaning, even the Torah could not reply, let the sinner regret his misdeeds and be atoned for, as in hataras nedarim, since the entire procedure of teshuva is one of mercy, beyond the boundaries of strict justice.

Why is teshuva considered such a chiddush [revelation], one that only Hashem Himself could have devised? The answer is as we said above, that when a man has already done a misdeed, even if he reaches a state of utter remorse for what he did, his misdeed nevertheless remains part of reality. What good will his remorse achieve? It won’t bring a murder victim back to life! Therefore, the Ramchal adds that teshuva is a “complete chessed.” (In fact, regret is enough to undo the act of rebelling against Hashem, but as for undoing the actual deed and reach a state in which it is as if the sin was never committed this requires Hashem’s chessed.)

It is for this reason that the nations feel that it is impossible to do teshuva. If you hurt someone, how can you undo that hurt? If you run a red light and get a ticket, will it help you to go to the judge and say: “I’m so sorry; I sincerely regret running that red light.” Will the judge forgive you? Is he allowed to? The court is based on the rule of law. What room is there for teshuva? All you can do is promise that you’ll be better in the future, but for the past, there’s no choice but to receive the punishment.

Hashem, however, gives us both parts of teshuva: there’s the teshuva that focuses on resolving to change in the future, to return to Hashem after having distanced ourselves from Him, and there is the teshuva that focuses on erasing the sin from the past. This is the avodah [work] of regretting our sins.

Once we better comprehend the awesome chessed Hashem has done for us with this gift of teshuva, we should realize automatically that as we do teshuva, we should have in mind always that the very concept of teshuva has no foothold in the world of justice, but is only a chessed of Hashem.