וַיַּגַּ֣ע עַל־פִּ֔י וַיֹּ֕אמֶר הִנֵּ֛ה נָגַ֥ע זֶ֖ה עַל־שְׂפָתֶ֑יךָ וְסָ֣ר עֲוֺנֶ֔ךָ וְחַטָּאתְךָ֖ תְּכֻפָּֽר׃
and he touched my mouth with it, and said: Lo, this hath touched thy lips; And thine iniquity is taken away, And thy sin expiated.
Read halakhic rulings (Jewish law) on Isaiah 6:7: and classical halakhic sources.