Regardless of the circumstances, Christianity in Nubia was linked to the Egyptian Church. It appears that the Nubian Church initially used the Greek language for religious rituals, then the Coptic language began to spread and be used in churches, and later the religious rituals were translated into the Nubian language. The period of prosperity for Christianity in Nubia was between the eleventh and thirteenth centuries. This is because the fourteenth century AD, the eighth century Hijri, witnessed the collapse of the two Nubian kingdoms, Alwa and Makuria. The kingdom of Alwa was richer than Makuria due to the vastness of its lands, its fertility, and the abundance of its provinces, which reached about nine provinces. When Ahmad ibn Sulaym al-Aswani visited the kingdom of Alwa during the Fatimid era, he found a ribat for Muslims there, which indicates the spread of Islam during that period of the seventh century Hijri, the thirteenth century AD. Ibn Sulaym al-Aswani also pointed out that until the end of the tenth century AD, Christianity had not yet taken root in the society of Southern Nubia. The vastness of the kingdom of Alwa and the availability of pastures and agriculture provided a vital area for the influx of Arab tribes flowing from the north. This provided an opportunity for the rulers not to resist the widespread Arab Islamic advance into their lands. The Arab tribes settled in these vast areas, by virtue of their customs and traditions, were the best to protect the inhabitants of Nubia, as many intermarriages took place between Arabs and Nubians, who welcomed these intermarriages as they guaranteed them strong support and protection amidst the factors of weakness and chaos that swept the country. Hence, the inhabitants of Nubia had no reason to prevent these Arab migrations or interfere in their affairs, especially since these arrivals from these Arab tribes did not cause the state or the population the slightest trouble or any disturbances. Especially since they worked to spread Islam on a wide scale.