Avos 4:1 הֱוֵי רָץ לְמִצְוָה קַלָּה

(2) Ben Azai says: Run to do an easy commandment as to a difficult one, and flee from sin; since a commandment leads to another commandment, and a sin leads to another sin; since the reward for a commandment is another commandment, and the reward for a sin is another sin.

(2) "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.

(1) "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.

(3) since the reward for a commandment is another commandment: This is a reason other than nature. And so he wants to say that the Holy One, blessed be He, did not give good or evil into the hand of a person; rather only choice, as it is stated (Deuteronomy 30:19), "and you shall choose life." And since he has chosen a path, if he is going in the good, God is with him. And [so] if he does one commandment, it helps him to do another commandment - as on his own, he doesn't even have the ability to do good. And about this it says, "since the reward for a commandment is another commandment, and the reward for a sin is another sin." And not, God forbid, that this is his reward. As if so, what reward does he [actually] have? And the thing is not like this, as his reward exists for the world to come. But rather he wants to say that the fruit of [doing] a commandment is [doing another] commandment; and he eats its fruits in this world, which is that it helps him to do other commandments. And it comes out that the principle expands and it exists in the world to come. And this is what is stated (Isaiah 3:10), "Hail the just man, for he is good; they shall eat the fruit of their works."

(2) and a sin leads to another sin: This too is natural. Since he has done one sin and distanced himself from the service of God, may He be blessed, when another sin comes to his hand - even if the impulse does not have a desire for it like for the first - he will do it; as his spirit is accessible to his impulse and it pushes upon it. And even if his desire is not great in the matter, he will do all of the sins; as his nature is used to 'doing every abomination towards God that He hates.'