Sanctify yourselves therefore,.... By abstaining from such impious and idolatrous practices, and separating themselves from all that gave into them, as well as by observing the holy commandments of the Lord; otherwise internal sanctification is not the work of man, but of the Lord himself, as in Leviticus 20:8,
and be ye holy; or a separate people from all others in worship and conversation:
for I am the Lord your God; who is a holy God, and therefore it became them to be holy, in imitation of him, Leviticus 19:2.

Sanctify yourselves therefore, and be ye holy--The minute specification of the incestuous and unnatural crimes here enumerated shows their sad prevalence amongst the idolatrous nations around, and the extreme proneness of the Israelites to follow the customs of their neighbors. It is to be understood, that, whenever mention is made that the offender was "to be put to death" without describing the mode, stoning is meant. The only instance of another form of capital punishment occurs in Leviticus 20:14, that of being burnt with fire; and yet it is probable that even here death was first inflicted by stoning, and the body of the criminal afterwards consumed by fire (Joshua 7:15).

For the Israelites were to sanctify themselves, i.e., to keep themselves pure from all idolatrous abominations, to be holy because Jehovah was holy (Leviticus 11:44; Leviticus 19:2), and to keep the statutes of their God who sanctified them (Exodus 31:13).