6 Men therefore shall see God, that they may live, being made immortal by that sight, and attaining even unto God; which, as I have already said, was declared figuratively by the prophets, that God should be seen by men who bear His Spirit [in them], and do always wait patiently for His coming. As also Moses says in Deuteronomy, “We shall see in that day that God will talk to man, and he shall live.” For certain of these men used to see the prophetic Spirit and His active influences poured forth for all kinds of gifts; others, again, [beheld] the advent of the Lord, and that dispensation which obtained from the beginning, by which He accomplished the will of the Father with regard to things both celestial and terrestrial; and others [beheld] paternal glories adapted to the times, and to those who saw and who heard them then, and to all who were subsequently to hear them.
Thus, therefore, was God revealed; for God the Father is shown forth through all these [operations], the Spirit indeed working, and the Son ministering, while the Father was approving, and man's salvation being accomplished. As He also declares through Hosea the prophet: “I,” He says, “have multiplied visions, and have used similitudes by the ministry (in manibus) of the prophets.” But the apostle expounded this very passage, when he said, “Now there are diversities of gifts, but the same Spirit; and there are differences of ministrations, but the same Lord; and there are diversities of operations, but it is the same God which works all in all.
But the manifestation of the Spirit is given to every man to profit withal.” But as He who works all things in all is God, [as to the points] of what nature and how great He is, [God] is invisible and indescribable to all things which have been made by Him, but He is by no means unknown: for all things learn through His Word that there is one God the Father, who contains all things, and who grants existence to all, as is written in the Gospel: “No man has seen God at any time, except the only-begotten Son, who is in the bosom of the Father; He has declared [Him].”
Source: Adversus haereses (New Advent)