"These are the Devarim / words that Moshe spoke to all Yisrael." (1:1) R' Yehuda He'chassid zt"l writes in Ta'amei Mesorot HaMikra: The word "Devarim / words," suggests "Devoirim" or "bees." The words of the Torah are like bees (and bee products). In other words, the Torah, especially Sefer Devarim which contains many harsh rebukes, are as sweet as honey to those who keep them, but will sting as painfully as a bee to anyone who mistreats them.
It is noteworthy that the Gematria of the word 'Mussar' = 306, which has the same Gematria as the word 'D'vash' (Honey), as well as, 'Av HaRachamon' (A reference to Hashem as our Merciful Father). Although Mussar may sting, ultimately it is as sweet as honey, and should be used to refine one's character and reaffirm our connection to our Merciful Father.