מדרש על ויקרא 19:27

3) (Vayikra 19:27) ("Do not round off the corners of your head, and do not destroy the corners of your beard.") "Do not round off" (plural): both the doer and the subject." "the corners of your head": the edges of your head, the temples on both sides.

4) "and do not destroy the corners of your beard": What is the intent of this? Because it is written (Vayikra 21:5) "and the corners of their beard they (Cohanim) shall not shave off," I might think that even cutting off with a scissors as with a razor makes him liable; it is, therefore, written "and do not destroy the corners of your beard." If (it were written only) "do not destroy the corners of your beard," I might think that even if he removed it with a tweezer or a depilatory it makes him liable; it is, therefore, written "and the corners of their beard they shall not shave off." How is this to be understood? As referring to shaving where there is destruction, i.e., (shaving with) a razor.

5) "the corners of your beard": the edges of your beard — so that he is liable, for the head, for two — one on each side; and for the beard, two on each side and one below. R. Elazar says: If he removed all of them as one, he is liable for only one (transgression).