Tertullian

“ Therefore the Father must be the face of the Son. For what does the Scripture say? “The Spirit of His person is Christ the Lord.” [16] As therefore Christ is the Spirit of the Father’s person, there is good reason why, in virtue indeed of the unity, the Spirit of Him to whose person He belonged—that is to say, the Father—pronounced Him to be His “face.” Now this, to be sure, is an astonishing thing, that the Father can be taken to be the face of the Son, when He is His head; for “the head of Christ is God.” [17] ”

“ Moreover, there comes to our aid, when we insist upon the Father and the Son as being Two, that regulating principle which has determined God to be invisible. When Moses in Egypt desired to see the face of the Lord, saying, “If therefore I have found grace in Thy sight, manifest Thyself unto me, that I may see Thee and know Thee,” [1] God said, “Thou canst not see my face; for there shall no man see me, and live:” [2] in other words, he who sees me shall die. Now we find that God has been seen by many persons, and yet that no one who saw Him died (at the sight) . ”

“ It will therefore follow, that by Him who is invisible we must understand the Father in the fulness of His majesty, while we recognise the Son as visible by reason of the dispensation of His derived existence; [3] even as it is not permitted us to contemplate the sun, in the full amount of his substance which is in the heavens, but we can only endure with our eyes a ray, by reason of the tempered condition of this portion which is projected from him to the earth. ”