Chain of Transmission

Sanad comes from the word Isnad; 

In Islam a list of authorities who have transmitted a report (hadith) of a statement, action, a teaching or approbation of Muhammad PBUH, of one of his Companions (Ṣaḥabah), or of a later authority (Tabieen); 

It determines  the validity or reliability of the teachings & is used to verify the legitimacy of a hadith or teaching.

This Sanad shows the Validity, reliability & credibility of my teacher (Sheikh Akbar's) teachings of Tafsir back to PBUH.

 Al-Imam Muhammad bin Sīrīn said: “Verily this knowledge is religion, so consider from whom you receive your religion.”