Concerning this, those who speak in parables say "Come to Heshbon...." [Chukat 21:27] In Maseches Bava Basra [78b], Chazal expound on this verse as follows: "Regarding this Hamoshlim would say - This refers to those who rule [hamoshlim] over their yetzer hara.  'Come to Cheshbon' - Come and let us make a calculation [cheshbon] of world importance."  This teaches us that it is incumbent