is one of the most elusive categories of hadith, for it can be uncovered only by the expert critics who investigate reports in both their isnads and their wording.

Ibn Hajar frequently says in Bulugh al-Maram, “It was declared defective because it is mursal,” or “It was declared defective because it is mawquf,” and the like. Whenever he makes such a remark, go back to the chain of transmission and see who actually narrated it.

For this reason the scholars stipulated that a hadith cannot be deemed sahih unless it is free from both shudhudh (irregularity) and any disqualifying hidden flaw. The muʿallal hadith is therefore a distinct branch of hadith methodology, and it is extremely important for the student of hadith: he may read a report whose outward appearance suggests soundness, while in reality it is not sound at all.