Musar על במדבר 21:27

"'therefore the rulers said, let us enter into an accounting' (Numbers 21:27). Therefore the rulers - of their [evil] inclinations said come and consider the accounting of the world - the loss incurred by doing a mitzva against the gain earned through it, and the gain obtained by doing a sin against the loss incurred..."

This reflection has varying degrees of arousing, respectively, for those of wholeness of understanding, those of lesser understanding, and for the general masses. Those of wholeness of understanding will be roused to watchfulness by their coming to see clearly that only perfection and nothing else is worthy of their desire, and that there is no greater evil than the lack of perfection and distance from it.

Therefore, they will choose only to maximize these means and to be stringent in all of their details, finding no rest or peace due to worry lest they possibly lack what will bring them to the perfection that they desire. This is what King Shlomo, peace be unto him, said: "fortunate is the man that fears always" (Mishlei 28:14), which our Sages explained (Berachot 60a) refers to matters of Torah.

We learned (Bava Bathra 78b): R. Shmuel b. Nachmani said in the name of R. Yonathan (Bamidbar 21:27): "Therefore, the rulers say: 'Let us come to Cheshbon, etc.': 'the rulers' — these are the rulers over their yetzer. 'Let us come to Cheshbon' — Let us come and make the world's accounting ['cheshbon' = account], the loss [entailed by the performance] of a mitzvah against its reward; and the reward of a transgression against its loss." The plain meaning is well known: this [the reward of a mitzvah] is forever, and this [the "loss" of a mitzvah] is temporal. Also, this [the "reward" of a transgression] is a negligible pleasure, and this [the reward of a mitzvah] is awesome. For "one moment of pleasure in the world to come is greater than all the pleasures of this world," and the opposite for transgression.