Abu Dawud
Jihad
Book Number: 008 / Hadith Number: 2585
Narated By Al-Bara' ibn Azib : Yunus ibn Ubayd, client of Muhammad ibn al-Qasim, said that Muhammad ibn al-Qasim sent to al-Bara' ibn Azib to ask him about the standard of the Apostle of Allah (pbuh). He said: It was black and square, being made of a woollen rug.