3. If a ḥadith is transmitted only through weak lines of transmission, their mere convergence does not necessarily raise it to the level of ḥasan. The weakness that stems from a narrator who is truthful and upright yet has a poor memory is remedied when the report reaches us by another route, so the ḥadith becomes ḥasan. The same holds when its flaw is due to irsāl (an interrupted chain); corroboration from another chain removes that defect as well. However, if the weakness arises from a narrator’s flagrant sinfulness, the agreement of other reports does nothing to improve the ḥadith’s status. Allah knows best.

The third category:
Al-ḍaʿīf (the weak ḥadith)
A weak ḥadith is any report that fails to satisfy the criteria of ṣaḥīḥ or ḥasan. Just as sound reports vary in strength, weak reports vary in degree of weakness. Some kinds have their own special designations, such as al-mawḍūʿ (fabricated), al-shādh (anomalous), and others.