Milhan bin Thawban (may Allah have mercy on him) says: Ammar bin Yasir (may Allah be pleased with him) was with us in Kufah for a year, and he used to deliver the Friday sermon to us every Friday while wearing a black turban.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5980