עַל כֵּן יֹאמְרוּ הַמֹּשְׁלִים בָּאוּ חֶשְׁבּוֹן תִּבָּנֶה וְתִכּוֹנֵן עִיר סִיחוֹן (כא, כז)
Therefore, the rulers say, "Come to Cheshbon, may it be built and established as the city of Sichon.” (21:27)
Chazal say (Bava Basra 78B) that “the rulers” refers to “those who rule over their desires.”
Sefer Zichron Shmuel asks what is meant by the first words of the verse “al ken” (“therefore”). What is this referring to?
He explains that a Jewish person must serve Hashem and retain control over his yeitzer hara. How can he do this? He must first recognize that every limb of the body is represented in the Upper Worlds. If one does an aveirah with one of his body parts, he is causing harm to that body part in the Upper World. If one thinks about this, he will be greatly ashamed of any sin he has committed. This is as the Mishnah states (Avos 2:1): “Dah mah l’mailoh mimcha. Know what is above you.” Tzadikim explain that the Mishnah can also be read to be saying: “Dah mah l’mailoh” – know that whatever happens Above” – “mimcha” – it is from you. In other words, your actions are the cause of events that occur in the Higher Worlds. This realization should shake up a person and cause him to commit not to listen to his yeitzer hara.
He thus explains that the words “al ken” are a reference to the happenings Above. They hint to the sphere of Hashem, as in the verse (Devarim 32:6): “Hu ascha v’yechonenecha.” He created and established you. When a person recognizes this, he will want to defeat the yeitzer hara. He will want to “go to Cheshbon”, meaning that he will have good thoughts (“machshavos”) of teshuva and mitzvos. Hashem will accept his teshuvah and good deeds and count them as a large “cheshbon” of good deeds (as good thoughts are rewarded by Him like actual actions), and he will be found to have more merits than aveiros.
He will then go on to be as established as “the city of Sichon”. The word “ihr”, city, can also mean “an enemy” (as Rashi explains that “arei Yisroel” can be a reference to the enemies of Klal Yisroel). The pasuk is teaching us that when a person is found to have more mitzvos than aveiros, even his enemies will defend him and speak well of him, as is stated in Chazal. This is seen from the word “Sichon”, which Chazal say is an acronym for “sicha na’ah” (nice words). This means that even our enemies, the prosecuting angels who want to harm us, will be forced to say nice things about us and to defend us.