The Rambam uncharacteristically adds a reason to the prohibition against cutting peyos. He says it is because the idol worshippers used to cut off their peyos.

More on Mitzvah Principles

All of Mitzvah Principles Acting on Inspiration Without Delay Bal Tosif Adding to Mitzvos Choosing a Day of Furlough From Prison Do Pomegranates Have 613 Seeds Doing a Mitzvah Yourself or More Beautifully Doing Part of a Mitzvah Ein Maavirin Al HaMitzvos Hiddur Mitzvah Versus Zerizus Is a Beautiful House a Mitzvah Joining Others in a Mitzvah Maakeh Roof Railing Mitzvah Items From Non-Kosher Animals Mitzvah Preparation Counts as a Mitzvah Not Delaying Mitzvos Reward for Inspiring Others Selling the Reward for a Mitzvah Sinning to Help Another Do a Mitzvah Sinning to Save Another From Sin Spending Money to Avoid a Sin Switching to a Nicer Mitzvah Item Tadir Kodem