According to Orbe's reconstruction of Irenaeus's views, there are two reasons why he would raise the issue of the filial adoption of Jesus' humanity against the Ebionites in Adv.
12) The variant occurs in the so-called `Western text," in the Gospel of the Ebionites, and in Justin, Clement of Alexandria, Methodius, Hilary, and in Latin manuscripts used by Augustine.
59) Orbe argues that Irenaeus here, at the end of three chapters on Jesus' baptism, is combating the views of the Ebionites, who understood the baptism as the time of Jesus' adoption as the Son of God ("?
76) For Orbe's summary of the Ebionite position, see "?
Sumney on Paul's opponents, and Petri Luomanen on the Ebionites
Additional chapters explore specific events and groups that shaped this history, such as the Christian change of the Sabbath from Saturday to Sunday, the enigmatic Christian sympathizers with Judaism known as Godfearers, and the mysterious Torah-observant Christian sects of Ebionites
Thus, making continuous references to proximate developments in Islam, Brown elaborates the adoptionist theology of the Ebionites
, their federal universalism, their critique of kingship as of the temple priesthood, and their notion of baptism as the primary emblem of purification rather than redemptive sacrifice--all with a view to understanding, with Schoeps, the world-historical "paradox" by which "Jewish Christianity indeed disappeared within the Christian church, but was preserved in Islam" (27).
Until the fourth century, sects of Christians (early on, the Ebionites
, and later, the School of Antioch, most importantly Diodorus of Tarsus and Nestorius) believed that Jesus was the biological son of Mary and Joseph and the adopted son of God.
Nowadays it has become almost conventional in this connection to propose the view that one or other "Jewish-Christian" community, such as the ancient Nazarenes, Ebionites
, or Elkasites, were present in Arabia, and that they exercised a decisive influence on Muhammad and the Qur'an.