Avos 4:2

"Since one commandment leads to another commandment": That is the way of the world, that one who does one commandment finds it easier to do others; and one who starts to do sins will find it difficult to separate from them. And also, "since the reward for a commandment is [another] commandment;" [meaning it] is from the Heavens that the one who does one commandment is helped and another commandment is placed in front of him to [also] do, in order to give him the reward for both of them. And so too, "the reward of a sin, etc." Another explanation: "since the reward for a commandment is [another] commandment;" Since all that a person is rewarded and derives enjoyment while doing a commandment is itself considered a commandment for him. And [so] he gets reward for the commandment that he did and for the enjoyment and benefit that he experienced in doing it.

"and the reward for one sin is another sin": And the reward and benefit that one derives from doing a sin is considered like a sin itself for him. And [so] he is [punished] for the sin that he committed and for the reward and benefit that he received by doing it.

"A sin": And we do not learn [here], "an easy [sin]," as we do with a commandment. Since that which we learned [concerning a commandment ], "easy," means that it is easy for person to do. And sins are easy for a person to do and most of them are enjoyable for people. Hence it is not applicable to teach, "from an easy sin" - Derekh Chaim.

We have already elucidated the explanation of this statement in Chapter 10 of Sanhedrin. And the sages, peace be upon them, have already brought attention to a wonderful innovation in the Torah in which there is inducement to the performance of the commandments. And it is its stating (Deuteronomy 4:41), "Then Moshe separated three cities in Transjordan, etc.," while knowing that they would not be effective - as they would not have the [status] of cities of refuge until the three others in the Land of Israel would be separated. They said (Makkot 10a), "Our teacher Moshe, peace be upon him, knew that these three cities in Transjordan do not shelter until the three cities in the Land of Israel would be separated, as it is stated (Numbers 35:13), 'they shall be six cities of refuge.' And he separated these nonetheless, since he said, 'Since a commandment has come to my hand, I will perform it.'" And if our teacher Moshe, peace be upon him - the fathomer of the truths, the [most] complete of the complete - was eager to add half of a positive commandment upon all of his rank and wholeness in this way, there is no need to say that those whose souls are leprous and their leprosy is strong and gaining should do [so].