1. Continuity of the chain of transmission;
2. Freedom from irregularity;
3. Freedom from a disqualifying defect.

Scholars have differed greatly over what counts as a disqualifying defect: one scholar may see in the ḥadīth a flaw that, in his view, demands rejection, while another may not deem that same flaw damaging at all.

For example, a person might suppose that a particular ḥadīth contradicts a stronger report, declare it irregular, and therefore refuse to accept it. Later, another researcher examines the matter, finds no real contradiction, and consequently judges the ḥadīth sound. The issue of hidden defects is subtle: the factor that removes the defect may escape one critic, leading him to fault the report, whereas another scholar perceives that factor and therefore raises no objection.

For this reason we added the proviso that the defect must in fact be disqualifying. A disqualifying defect is one that touches the very substance of the ḥadīth; a flaw that lies outside its subject-matter is not so regarded.

Consider, for instance, the report of Fadalah ibn ʿUbayd (may Allah be pleased with him) about the gold necklace sold for twelve dinars—the dinar being a gold coin. When the necklace was dismantled, the gold in it was found to exceed twelve dinars.¹

The narrators disagreed over the exact price:
– some said twelve dinars;
– others said nine dinars;
– and others said ten dinars.