How should we classify a hadith that was authentic in the time of a classical scholar like Imam Abu Haneefa but later became weak? What I mean is: suppose that for a particular hadith, the narrators between Prophet Muhammad, sallallaahu ‘alayhi wa sallam, and Imam Abu Haneefa were all trustworthy and had an excellent memory, and so Imam Abu Haneefa classified that hadith as authentic, but later on, when other narrators narrated from Imam Abu Haneefa, it was found that one or more of them had poor memory or were not reliable. Now, can this hadith be classed as weak because of the unreliable narrator(s) that followed Imam Abu Haneefa in the chain?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

The supposition suggested by the dear questioner is not possible. He supposes that one of the classical scholars narrated a hadeeth on the authority of the Prophet, sallallaahu ‘alayhi wa sallam, with an authentic chain of narration and then someone who came after the time of that classical scholar narrated the same hadeeth on the authority of the classical scholar but with an inauthentic chain of narration and accordingly the hadeeth would be rejected after having been accepted earlier. This is a false deduction because the authenticity of the ahaadeeth narrated by the Imaams with an authentic chain of narration can be established in two ways only:

The first is that the Imaam cited the chain of narration of the hadeeth in his Hadeeth collection (Musannaf), and in this case there is no need for the other version of the hadeeth narrated by the later day person with the inauthentic chain of narration on the authority of this Imaam. The second is that a trustworthy narrator narrated this hadeeth on the authority of this Imaam with an authentic chain of narration. In both cases, the hadeeth would still be authentic and will not be rejected after having been accepted.

Allaah knows best.