13 The beginning of this madness was Arius (whose name is derived from frenzy), who paid the penalty of his unbridled tongue by his death in a profane spot, brought about by prayer not by disease, when he like Judas burst asunder for his similar treachery to the Word. Then others, catching the infection, organized an art of impiety, and, confining Deity to the Unbegotten, expelled from Deity not only the Begotten, but also the Proceeding one, and honoured the Trinity with communion in name alone, or even refused to retain this for it.
Not so that blessed one, Who was indeed a man of God and a mighty trumpet of truth: but being aware that to contract the Three Persons to a numerical Unity is heretical, and the innovation of Sabellius, who first devised a contraction of Deity; and that to sever the Three Persons by a distinction of nature, is an unnatural mutilation of Deity; he both happily preserved the Unity, which belongs to the Godhead, and religiously taught the Trinity, which refers to Personality, neither confounding the Three Persons in the Unity, nor dividing the Substance among the Three Persons, but abiding within the bounds of piety, by avoiding excessive inclination or opposition to either side.
Source: Orations (New Advent)