Asalam ul laykum dear brothers and sisters. It is very important to nite when observing these works of the MiddleAges is that Arabs bedoiuns were a poor community and that meaning of writting resources in those times were very expenaive. So when the scribe sahabas wrote down on parchments during time of prophet muhammad pbuh, those were reused materials. Meaning like a skin of a goat that previously had writtings on it and had to be cleaned so to have no writting and then be reused for preserving Quran. The scholars nowaday use carbondating scans which allows to see if there were ever other text on the material. This however, is irrelevant because many times in old works same materials were reused because materials were expensive and low in availability.
That aside the oldest work is the birmibgham portfolios that contain surah taha, which comes from time of prophet muhammad pbuh. Only some orientalist scholars with agenda argue that the material is few years older then life of prophet muhammad pbuh. However they do not take in account the life of the animal and the entire life of where that material comes from. These arguments were presented by brother adnan rashid, who is a historian and scholar of islam. These r valid arguments because all of these important facts have to be looked at when examining acient historical works.
Jazakallah.
