isnād, (from Arabic sanad, “support”), in Islam, a list of authorities who have transmitted a report (hadith) of a statement, action, or approbation of Muhammad, of one of his Companions (Ṣaḥābah), or of a later authority (tabiʿī); its reliability determines the validity of a hadith.

In the Quran and hadiths it is used in a number of senses, including 'Lord', 'guardian', and 'trustee'.[1]