Musannaf Ibn Abi Shayba 38:169

Ghundar narrated to us, from Shu'bah, from 'Amr ibn Murrah, from Mus'ab ibn Sa'd, who said: I asked my father about this verse: "Say, 'Shall we inform you of the greatest losers as to [their] deeds? [They are] those whose effort is lost in worldly life,'" (18:103-104). Are they the Haruriyyah? He said: No, they are the People of the Scripture, the Jews and the Christians. As for the Jews, they denied Muhammad, may Allah bless him and grant him peace. And as for the Christians, they disbelieved in Paradise and said: "There is no food or drink in it." But the Haruriyyah are "those who break the covenant of Allah after its ratification and sever that which Allah has ordered to be joined and cause corruption on earth. It is those who are the losers" (2:27). And Sa'd used to call them the defiantly disobedient (al-fasiqin).