Sahih Muslim Book - 0, Hadith - 27

حَدَّثَنَا أَبُو جَعْفَرٍ مُحَمَّدُ بْنُ الصَّبَّاحِ حَدَّثَنَا إِسْمَاعِيلُ بْنُ زَكَرِيَّاءَ عَنْ عَاصِمٍ الْأَحْوَلِ عَنْ ابْنِ سِيرِينَ قَالَ لَمْ يَكُونُوا يَسْأَلُونَ عَنْ الْإِسْنَادِ فَلَمَّا وَقَعَتْ الْفِتْنَةُ قَالُوا: سَمُّوا لَنَا رِجَالَكُمْ فَيُنْظَرُ إِلَى أَهْلِ السُّنَّةِ فَيُؤْخَذُ حَدِيثُهُمْ وَيُنْظَرُ إِلَى أَهْلِ الْبِدَعِ فَلَا يُؤْخَذُ حَدِيثُهُمْ.

It is narrated that Ibn Sirin said, "They used not to ask about the chain (of narrations), but when the Fitnah occurred, they said, 'Tell us about the men (in the chain of narrations).' They would look for the people following Sunnah to accept their Hadith, and they would look for the people following Bidah (innovations in religion) to reject their Hadith."