787 - Harb ibn Isma'il al-Kirmani informed me, saying: Abu Bakr Hammad ibn al-Mubarak narrated to us, saying: Muhammad ibn Haytham narrated to us, saying: al-Walid ibn Muslim narrated to us, from Thawr ibn Yazid, from Khalid ibn Ma'dan, from Mu'adh ibn Jabal, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "When innovations appear and my companions are reviled, it is incumbent upon the scholar to manifest his knowledge; whoever does not do so, upon him shall be the curse of Allah, the angels, and all of mankind." He said: I asked al-Walid, "And what is the manifestation of his knowledge?" He replied, "The Sunnah." He said: And Abu Bakr ibn Ayyash and 'Abbad ibn al-'Awwam were asked [the same], and they said, "The Sunnah."