The Sma"g writes that the 620 letters of the Ten Commandments correspond to the crown of 613 Torah-level Mitzvos plus the 7 Rabbinic-level mitzvos (620 = כתר)
The Chasam Sofer writes that the seven Rabbinic-level mitzvos are alluded to in the last two words (seven letters) of the Ten Commandments (Prior to the last 7 letters, there were 613 letters in the Ten Commandments)
"אשר לרעך" - "Asher lereiecha” (20:14) – “That belongs to your friend”
Seven Rabbinic-level Mitzvos
- א "aveilus" אבילות; mourning a death
- ש "simchah" שמחה; rejoicing with a groom and bride for 7 days
- ר "rechitzah" רחיצה; washing one's hands before partaking of bread
- ל "lechem" לחם ; the prohibition against eating "pas akum" (and "bishulei akum")
- ר "reshuyos" רשויות (domains); the requirement to create "eiruvei chatzeiros" and "shitufei mevuos" for Shabbos
- ע Amalek עמלק; reading Megilas Esther on Purim (a remembrance to blot out Amalek)
- ך Kohanim כהנים ; the institution of Chanukah lighting (based on the actions of the Kohanim)
The last 7 letters refer to the Oral Torah, as Hillel referenced when he told the potential convert רעך.
The count of 620 words in of the version in Parshas Yisro. The version in Parsha Ve’eschanan has 707 letters.
The Chovas Halevavos explains that fulfillment of Mitzvos associated with the heart are not defined by a specific quantity; as every day one can understand more and more about HaShem’s greatness, and therefore, love Him more, for example.
