It is reported about Sayyiduna Ali (may Allah be pleased with him) that on a Friday he delivered the sermon on the pulpit, and al-Ash'ath stood up before him and said: These red-complexioned ones (the non-Arab clients) have overcome us with regard to you. Sayyiduna Ali (may Allah be pleased with him) said: "Who will excuse me regarding these worthless people? One of them stays behind, turning over on his bed, while those others hasten to the remembrance of Allah. If I were to drive them away, then in that case I would be among the wrongdoers. By Allah! I heard him say: 'They will certainly fight you on the basis of the religion, just as you at first fought them on the basis of it (the religion).'"
Abu Ya'la recorded it; its chain contains a narrator, Abbad bin Abdullah al-Asadi, whom Ibn Hibban declared thiqah (trustworthy), while al-Bukhari (may Allah have mercy on him) said: There is room for consideration about him (fihi nazar).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الفتن - أعاذنا الله منها / 12029