John 3:16-17

Give his only begotten Son --- God sent not his Son into the world. He was then his Son, his only begotten Son, before he sent him into the world. He was not, therefore, his Son, only by the incarnation, but was his Son from the beginning, as he was also his word from all eternity. This was the constant doctrine of the Church, and of the Fathers, against the heresy of the Arians, that God was always Father, [1] and the Son always the eternal Son of the eternal Father. See note on chap. i. ver. 14. (Witham) --- The world may be saved. Why, says St. Augustine, is Christ called the Saviour of the world, unless from the obligation he took upon himself at his birth? He has come like a good physician, effectually to save mankind. The man, therefore, destroys himself, who refuses to follow the prescriptions of his physician. (St. Augustine)

[BIBLIOGRAPHY]

Greek: Aei Theos, aei uios; ama pater, ama uios. Arius began his heresy by denying this, as it appears in his letter to Eusebius, of Nicomedia, in St. Epiphanius, hær. 69, p. 731.