Or HaChaim on Leviticus 20:2/אור החיים על ויקרא כ׳:ב׳

1 ואל בני ישראל תאמר, "Moreover, you shall say to the children of Israel, etc." The reason for the expression "and to the children of Israel" is that all of them are to be involved in executing anyone who hands any of his children to the fire-god Molech. The conjunctive letter ו at the very beginning of the paragraph hints that not only the person who delivers a child to the Molech is guilty of punishment but also those who fail to punish such a person.