If they argue with you, say only: "God knows well what you are doing. (To me are accounted my deeds, and to you, your deeds. You are quit of all that I do, and I am quit of all that you do.)"
If they argue with you say, “Allah (as the creator) knows best what you do.”
Sayyed Abbas Sadr-Ameli
And if they dispute with you, say: �Allah knows best what you do�
Al-muntakhab fi tafsir al-Qur'an al-Karim
And should they -the infidels- be tossed in their unballasted wits in fathomless and unquiet deeps of controversy, then say to them: "Allah knows best what you do"