question #1 Sahih Muslim Introduction 19, Introduction, Narration 18 : What criteria did Ibn Abbas use to evaluate the authenticity of hadith narrations?

‘Go back to such-and-such narration‘. Then [Bushayr] returned to it and narrated it. So [Ibn Abbās] said to him: ‘Go back to such-and-such narration’. Then [Bushayr] returned to it and narrated it. Thus [Bushayr] said to him: ‘I do not know whether you know all of my Ḥadīth and you reject this one and that, or if you reject all of my Ḥadīth and know this one and that?’ Ibn Abbās said to him: ‘Indeed we would be narrated to on authority of the Messenger of Allah, peace and blessings of Allah upon him, at a time when one would not lie upon him, however when the people took the difficult [Munkar] and the docile [Sahīh], we abandoned listening to Ḥadīth from them’.