What are the reasons for the existence of weak hadiths in the books of the early scholars, and how do we deal with them?

Weak hadiths are divided into three categories:

1. Hadiths that are definitively rejected and whose attribution to the Prophet, peace and blessings be upon him, is deemed false: These are hadiths that came through mendacious or accused narrators, or those who were severely weak and had poor memories, and whose text shows oddity (munkar), or those where the narrator is definitively known to have erred due to contradicting more trustworthy narrators. Such hadiths are only mentioned to highlight their weakness.

2. Weak hadiths due to the presence of a weak or unknown narrator, or a slight discontinuity in the chain of transmission, without any oddity (munkar) in the text: Scholars do not definitively reject these, but rather consider the possibility of their emanation from the Prophet, peace and blessings be upon him, as still existing. They accept them if corroborating evidence strengthens them, such as multiple chains of transmission. Scholars mention them for anecdotal purposes, not for drawing legal inferences, in chapters concerning stories, softeners of the heart (raqa'iq), and virtues of deeds, considering the possibility of their truthfulness, or in imitation of those who preceded them, or with an indication of their weakness using weakening formulations (sigh al-tamreedh).

3. Disputed hadiths: These oscillate between weakness and being sound (hasan) or acceptable (maqbool). Scholars mention them to account for the difference of opinion regarding them or to prefer their acceptance. The possibility of error remains, even for the imams of hadith.