The Christians in pre-Islamic Arabia fewer and less better organized than the Jewish communities. They were more recent occupants who penetrated in the peninsula towards IIIème century after J-C.
The first group was that of Abyssins which was distributed between mercenaries and slaves with the service of the Arabs, in particular in Mecca.
The second group was that of Nabataeans (`Al Ambat) originating in Petra. They were specialized in the trade of corn, the olive oil and the wine.
They were subjected to a tax, the gizya, which was a tax per capita on the foreigners resident in exchange of the protection of the Arabs of Mecca.
It’s probable that there were also christianized Arabs established in Arabia for a long time.
The main Christian establishment was Najran, close to the borders of Yemen. They was Christians Monophysites, therefore of Syrian origin, who had their bishop.
The Christian world of the first centuries was shaken several dissidences and theological debates were worked out then took certain acuity during the conversion of the Byzantine emperor Constantin into 313 then into 384 when Christianity became the official religion with Théodose.
From this time, the amalgam was done between religion and fidelity with the emperor of Byzance. The schisms and repressions followed one another. The tensions became very strong in the middle of 6th century during the reign of Justinian the Great.
the Christian hierarchy of Greek origin was opposed to the popular Christianity of not-Greek culture (Aramaeans, Coptic-Christians…).
The first great controversy was that of the Arianism. Arius taught and said that the pre-incarnate Jesus was a divine being created by God and probably inferior to Him at some point. The council of
Nicaea condemned the arianism and worked out the dogma of the Trinity according to which God, Christ and the Holy Spirit were the expression of only one divine person. The arianism settled nevertheless in Balkans and a little in Western Europe (Visigoths in particular).
The second great controversy is engaged by Nestorius Patriarche of Constantinople (Byzance). Nestorius posed the principle of the separation of divine and human natures of Christ. It was at the same time a dispute of the dogma of the incarnation according to which God was made man in the person of Jesus Christ and the dogma of the redemption since according to Nestorius only the human nature of Christ had died on the cross.
The council of Ephesus of 431 condemned Nestorius. His partisans took refuge in the Sassanid empire (in particular current Iraq.)
The third controversy was that of the monophysism. Eutyches said that after the crucifixion of Jesus there remained only his divine nature, the divine one having then absorbed the human one. The council of Chalcedon condemned the monophysism and excommunicated Eutyches. The monophysism triumphed in Armenia, in Syria, in Egypt and in Sudan.
The pre-Islamic Arabs were thus with the direct contact of the Christians and more particularly of the dissidents monophysites and nestorians.