Ijaza
The licence of transmission: the document or act by which a holder authorises someone to transmit a knowledge or a charge.
Ijaza comes from the root j-w-z, ‘to make lawful’: it is the licence by which a master authorises someone by name to transmit what he himself received. The institution predates the brotherhoods: in hadith scholarship, the ijaza attested that a scholar had heard a given collection from its author’s mouth or from an approved transmitter.
In the Sufi paths, the ijaza extends the same logic: written or oral, it names the recipient, specifies what he is authorised to transmit, and recalls the silsila within which that transmission falls. It is the documentary proof of the idhn. The archives of the great tariqas keep these certificates, some going back to the Middle Ages.
For the researcher the distinction is practical: the idhn is the authorisation itself, the ijaza its attestation. An authentic guide can always say who authorised him and show the continuity of his chain, as the initiatic chain of the Qadiriya Boutchichiya does.