Early Trinitarian Sources

Here are some of the earliest references to the Trinity:

Theophilus of Antioch (180 AD), in his To Autolycus, discusses the shape of God's creative activity as Father, Logos and Sophia. Here is a quote:

• "He is God, who heals and gives life through Logos and Sophia. God made everything through Logos and Sophia, but by his Logos the heavens were made firm and by his Spirit all their power [Ps 32:6]." Theolophilus of Antioch, Ad Autolycum, tr. by Robert M. Grant, Oxford: Claredon Press, 1970, I.7.
  

In another place, he says:

• "the three days prior to the luminaries are types of the triad of God and his Logos and his Sophia. In the forth place is man, who is in need of light--so that there might be God, Logos, Sophia, Man." (the footnote to this: "This 'triad' is not precisely the Trinity, since in Theolophilus' mind man can be added to it.") Theolophilus of Antioch, Ad Autolycum, tr. by Robert M. Grant, Oxford: Claredon Press, 1970, II.15.
  

Though this is not a perfect articulation of trinitarian theology, you can see how Theolophilus is attempting to put words and concepts to something that was already believed in early Christendom.

Another source of early trinitarian thought is Irenaeus of Lyon (125-203). He also talks about God creating through the Logos and Wisdom (Sophia), but more specifically talks about the Son and the Holy Spirit as the two hands of the Father:

• "It was not angels...who made us, nor who formed us, neither had angels power to make an image of God, nor any one else, except the Word of the Lord, nor any Power remotely distant from the Father of all things. For God did not stand in need of these [beings], in order to the accomplishing of what He had Himself determined with Himself beforehand should be done, as if He did not possess His own hands. For with Him were always present the Word and Wisdom, the Son and the Spirit, by whom and in whom, freely and spontaneously, He made all things..." Ireneaus, "Against Heresies," in Ante-Nicene Fathers, vol. 1, Edinburgh: T&T Clark; Eerdmans, 1996, Book IV: chapter XX.1.

I hope this helps. If anyone wants to pursue other sources, let me know.

Peace,
Chelle