The word 'incarnation' was coined for Jesus but spread far beyond him
'Incarnation' literally means taking on flesh, and the noun was first made to describe how Christians believe God became human in Jesus. Yet the idea turns up in a Fatimid caliph revered by the Druze, an Ethiopian emperor honoured by Rastafarians, and the Hindu avatar, whose name means 'descent'. Other faiths reject it outright.
For Christianity the doctrine is central: God the Son, the second person of the Trinity, became a man in Jesus, conceived in the womb of the Virgin Mary. His divine and human natures are held to be perfectly joined in one person, truly God and truly human, a union theologians call hypostatic. Traditional supporting texts include passages in John, Colossians and Philippians.
Other Abrahamic traditions mostly say no. Since Maimonides, mainstream Judaism has largely ruled out any incarnation of God, and Islamic theology rejects it categorically. The Baháʼí Faith holds that God cannot be divided or descend into creation; its Manifestations of God are pictured as flawless mirrors reflecting divine attributes, not God in the flesh. Even so, many modern scholars read the Bible and Talmud as picturing God in human-like terms, sometimes appearing bodily, and some Hasidim hold that a rebbe carries God's essence in a righteous person's body.
Two smaller faiths make the claim explicitly. Hamza ibn Ali, regarded as the Druze founder, taught that God took human form as the Fatimid caliph al-Hakim bi-Amr Allah, whom ad-Darazi proclaimed God incarnate in 1018; Druze belief expects al-Hakim to return to judge the world. Rastafarians traditionally regard Haile Selassie I, Ethiopia's emperor from 1930 to 1974, as Jah incarnate or the Second Coming, though some see him instead as a prophet. Rastafari also stresses that Jah dwells partly in every person, captured in the phrase 'I and I'.
In Hinduism the concept appears as the avatar, a word meaning descent or making an appearance, with overtones of crossing over. Scholar Daniel Bassuk reads the imagery as the divine moving from eternity into time and from the infinite into the finite. Hindu thought also uses incarnation for its doctrine of rebirth.
Source: Incarnation