قيصر
Qayṣar
The title the Arabs used for the Byzantine emperor, “Caesar of Rome”.
What it means
In the hadith the Prophet writes to Heraclius as “the great one of the Romans”, and Qaysar is used for the emperor of Constantinople. A hadith in Sahih al-Bukhari says the first army to attack “the city of Caesar” would be forgiven, which Muslim scholars connected with the early sieges of Constantinople.