What are the conditions for a Sahih Hadith?

A sound hadith has two applications: a general one that includes the mutawatir, the sahih li-dhatihi, the sahih li-ghayrihi, and the hasan; and a specific one that includes the sahih li-dhatihi and the sahih li-ghayrihi. Its specific definition is that which is narrated by an upright person (‘adl), of perfect retention (tāmm al-ḍabṭ), with a continuous chain of transmission (sanad muttaṣil), free from shudhudh (aberrance) or ‘illah (defect). The conditions for a sound hadith are five: the uprightness of the narrators, their perfect retention, the continuity of the chain of transmission, freedom from shudhudh, and freedom from ‘illah. These conditions have been agreed upon by scholars, although some have been lenient with certain aspects, such as the mursal (missing link in the chain) or the mudallas (concealed defect). The disagreement among scholars regarding the authentication of hadiths arises from their differing views on the conditions of soundness or their applicability to a specific hadith. These conditions are logically sound in their purpose and represent the culmination of scholarly efforts.