Sahih Muslim — Hadith #7590

Abu Ja'far Muhammad ibn al-Sabbah narrated to us that Isma'il ibn Zakariyya narrated to us from Asim al-Ahwal, who narrated from Ibn Sirin. Ibn Sirin said: They used to not ask about the chain of narrators. When the fitna (strife/discord) arose, they began to say: Tell us the names of your narrators. Now, attention is paid to the Ahl as-Sunnah, and their hadiths are accepted; attention is paid to the Ahl as-Bid'ah, and their hadiths are not accepted.