There is the law in Leviticus, You cannot shave the corners of your beard.

You, son of man, take a sharp sword You shall take it as a barber's razor to you, and shall cause it to pass on your head and on your beard then take balances to weigh, and divide the hair.

And thou, son of man, take thee a sharp knife, take thee a barber's rasor, and cause it to pass upon thine head and upon thy beard then take thee balances to weight, and divide the hair.