Eutychius, Patriarch of Alexandria
Patriarch Eutychius wrote his Annals and his The Book of the Demonstration during the period of Muslim occupation, providing a rich collection of references to the history of the church and the sanctuaries of the Holy Land in that era. In his Annals he mentions the story relating to Caliph Omar who, according to tradition, shortly after the conquest of Bethlehem (7th century) had prayed in the church, which then became a place of worship also for Muslims.
Caliph Omar prays at the Church of the Nativity
So Omar built a temple and set the stone in its back part. From there he went to see Bethlehem. When the time of prayer came, he prayed inside the church, at the south arch. This arch was completely decorated with mosaics. Omar wrote a charter for the patriarch forbidding Mohammedans to pray in that place except one at a time, one after the other, and forbidding their meeting there for prayer, or being called together by the voice of a crier; and he forbade any part of this charter to be altered.
Eutychius (Said ibn Batriq), Annals (sec. X)