then I will set My face against that man and his family and cut off from among their people both him and all who follow him in prostituting themselves with Molech.
Moses is here directed to say that again to the children of Israel which he had in effect said before, Lev 20:2. We are sure it was no vain repetition, but very necessary, that they might give the more earnest heed to the things that were spoken, and might believe them to be of great consequence, being so often inculcated.
Commenting on Leviticus 20:1-9
Then I will set my face against that man,.... That man that sees him do the fact, and winks at it, or the judge that connives at him, and will not condemn him, as well as the man that has committed the iniquity: and against his family; either the family of the witness, who could and should have testified against him, or of the judge...
Lev 20:4-5 If the people, however (the people of the land), should hide their eyes from him (on the dagesh in חעלּם and יעלּימוּ see the note on Lev 4:13-21), from an unscrupulous indifference or a secret approval of his sin, the Lord would direct His face against him and his family, and cut him off with all that went a whoring after him.
Commenting on Leviticus 20:4-5