Uways al-Qarani (in Anatolian folk culture Veysel Karani) was a Yemeni ascetic of the Tabi'un; though he never met the Prophet, he was famed for his deep devotion and is regarded as the master of the 'Uwaysi' path. By tradition he was martyred in Ali's army at Siffin (37/657) and buried near Raqqa, though his burial is disputed, with Raqqa most probable. The mosque and shrine were destroyed by ISIS in 2013-2014 and not rebuilt. (Sources: TDV 'Veysel Karanî'; Wikipedia.)