question #1 Sahih Muslim Introduction 27, Introduction, Narration 26 : Why is it important to verify the chain of narrators in hadith transmission?

‘They would not ask about the chains of narration, and when the Fitnah occurred, they said: ‘Name for us your men’. So Ahl us-Sunnah would be regarded, and their Ḥadīth were then taken, and Ahl ul-Bi’dah would be regarded, and their Ḥadīth were not taken’.