27You shall not round off the hair on your temples or mar the edges of your beard.
The context of Leviticus 19:27–28 is pagan mourning rituals. The Hebrews are not to cut the sides of their heads or mar their beards, common Canaanite practices (Deuteronomy 14:1).
27 You shall not round off the hair on your temples or mar the edges of your beard.