Midrasz do Kapłańska 20:7

2) (Vayikra 20:7) "And you shall sanctify yourselves and you shall be holy": This is the holiness of separation from idolatry. You say that it is the holiness of separation from idolatry, but perhaps it is the holiness of (performing) all of the mitzvoth! — "Holy shall you be" (Vayikra 19:2) already speaks of the holiness of all the mitzvoth. "And you shall sanctify yourselves and you shall be holy," then, must refer to the holiness of separation from idolatry. (Vayikra 19:7) "For I am the L–rd your G d": I am the Judge, exacting (punishment) and trusted to reward.