The passuk states ומל ה’ אלוקיך את לבבך ואת לבב זרעך לאהבה את ה’ which literally means “and Hashem will circumcise your heart and your offspring’s heart to love Hashem.” What is the meaning of Hashem circumcising the heart?
Onkelos translates the word ומל as and remove, and adds the word טפשות which means “foolishness” or as the Radak explains “fattiness.” The passuk then means: Hashem will remove the foolishness and fattiness of your hearts and your offspring’s heart. What is this foolishness and fattiness which Hashem will remove, and what is the purpose of removing it?
The Nefesh HaGer explains that this is as the Gemara brings: a person only sins because a spirit of foolishness has entered into him. This refers to the yetzer hara which enters into a person, stuffs up his heart and convinces him to do aveiros. Moshe Rabeinu called the yezter hara ערל, as it states ומלתם את ערלת לבבכם. Onkelos translatesערל as foolishness or fattiness. The passuk means that you shall remove the foolishness and fattiness of your heart to stop yourselves from sinning.
The Ramban explains that from the beginning of creation a person had free will, to become a tzaddik or a rasha, in order to allow him to be rewarded if he chooses good or be punished if he chooses bad. Originally the options to do good or bad were not equal, rather it was natural to do what was proper and fitting. Once Adam sinned this changed, there became a mixture of good and bad, and desires for unfitting things. However in the days of Mashiach it will return to the level as was before Adam’s sin, and one’s heart will naturally feel interested in choosing to do what is proper and good, and it will not desire that which is improper or unfitting. The Torah states והשבתי חיה רעה מן הארץ. The Ramban brings: Rebi Shimon explains, in the future Eretz Yisrael will return to the level at the beginning of creation before Adam HaRishon sinned and Hashem will annul the wild animal’s wild nature and therefore they will not kill or injure. There will be a natural feeling by the entire creation to do good.
The מילה stated here refers to the removal of ones desires and lusts, thereby annulling the yetzer hara. This is as it states in Yechezkel, ונתתי לכם לב חדש ורוח חדשה אתן בקרבכם and I will give you a new heart and a new spirit I will put in you. The new heart hints to the natural interest to do that which is fitting.
The Rabbeinu Yonah explains differently; this passuk refers to doing teshuvah. If a person repents, Hashem will remove the foolishness and fattiness of the ערלת הלב and Hashem will implant within him a spirit of purity even above his true nature to come closer to Hashem.
May Hashem remove the foolishness and fattiness of our hearts and bring us back to fulfill the razton Hashem naturally!