حَدَّثَنَا أَبُو جَعْفَرٍ مُحَمَّدُ بْنُ الصَّبَّاحِ، حَدَّثَنَا إِسْمَاعِيلُ بْنُ زَكَرِيَّاءَ، عَنْ عَاصِمٍ الْأَحْوَلِ، عَنِ ابْنِ سِيرِينَ، قَالَ: «لَمْ يَكُونُوا يَسْأَلُونَ عَنِ الْإِسْنَادِ، فَلَمَّا وَقَعَتِ الْفِتْنَةُ قَالُوا: سَمُّوا لَنَا رِجَالَكُمْ، فَيُنْظَرُ إِلَى أَهْلِ السُّنَّةِ فَيُؤْخَذُ حَدِيثُهُمْ، وَيُنْظَرُ إِلَى أَهْلِ الْبِدَعِ فَلَا يُؤْخَذُ حَدِيثُهُمْ».
Translation: Abū Jaʿfar Muḥammad b. al-Ṣabbāḥ related to us from Ismāʿīl b. Zakariyyāʾ, from ʿĀṣim al-Aḥwal, from Ibn Sīrīn, who said: “They did not use to ask about the chain of transmission. But when the fitnah occurred, they said: Name your transmitters for us. The people of the Sunnah were then examined and their reports accepted, while the people of innovations were examined and their reports not accepted.”
“They would not ask” describes an earlier general practice, not the claim that nobody ever checked a source. During and after turmoil the demand to name transmitters became systematic. This passage alone does not fix a single undisputed date for the fitnah.