“Look for Him who is above all time, eternal and invisible, yet who became visible for our sakes; impalpable and impassible, yet who became passible on our account; and who in every kind of way suffered for our sakes.” Ignatius, Epistle to Polycarp Shorter Version, chapt. 3.
Ireneaus of Lyons (born between 115 and 125)
“Now God shall be glorified in His handiwork, fitting it so as to be conformable to, and modelled after, His own Son. For by the hands of the Father, that is, by the Son and the Holy Spirit, man, and not [merely] a part of man, was made in the likeness of God.” Irenaeus of Lyons, Against Heresies, Book V.VI.1.
“As if in this way also one were not All, in that All are of One, by unity (that is) of substance; while the mystery of the dispensation is still guarded, which distributes the Unity into a Trinity, placing in their order the three Persons — the Father, the Son, and the Holy Ghost: three, however, not in condition, but in degree; not in substance, but in form; not in power, but in aspect; yet of one substance, and of one condition, and of one power, inasmuch as He is one God, from whom these degrees and forms and aspects are reckoned, under the name of the Father, and of the Son, and of the Holy Ghost. How they are susceptible of number without division, will be shown as our treatise proceeds.” Tertullian, Against Praexis, chapt. 2. (The whole of this treatise is Trinitarian.)
“For even although something else existed before the Holy Spirit, it was not by progressive advancement that He came to be the Holy Spirit; as if any one should venture to say, that at the time when He was not yet the Holy Spirit He was ignorant of the Father, but that after He had received knowledge He was made the Holy Spirit. For if this were the case, the Holy Spirit would never be reckoned in the Unity of the Trinity, i.e., along with the unchangeable Father and His Son, unless He had always been the Holy Spirit.” Origen, de Principiis, I.III.4.