Ibn Al-Muhallab reports that he heard Abȗ Mȗsâ Al-Ash’arî – Allah be pleased with him – standing on his minbar (pulpit) saying:

Whoever Allâh has given some knowledge should teach it. And he must not say anything he has no knowledge of, lest he become one of the pretenders and leave the religion.

Ibn Sa’d, Al-Tabaqât 4:102. Maktabah Al-Khânjî, Cairo.