The word “Trinity” is not found in the Bible. Nor is homoousios which is the key concept that was agreed on at the first ecumenical council at Nicaea in 325 affirming that God the Son and God the Father are of the same substance (the God stuff!).
Don’t worry about that stuff! We worship One God but three Persons. One God inclusive of the Son whom we saw, and who spoke of the Father and the Spirit – the Advocate. What is most important in this doctrine of Trinity is that we find our model for community. As God the Father, the Son, and the Spirit relate to one another, demonstrate love for each other, and work in concert to accomplish the purpose of God in the world, we get the idea of community.
God is the primordial model of all community life. In God each divine Person gives completely to the other. When God gives, nothing is left in the tank. This process of self-emptying and being given to the other is how God is, was, and will always be. And this is equally how we should relate to one another by the complete gift of myself to yourself; nothing held back, no reservations. In other words we need to strive to have undivided and magnanimous hearts. In heaven we will have been purified enough to give of ourselves in this way with undivided hearts.
This point leads us back to the fact that the revelation of the Trinity is proof of God’s love for us. We do not reveal ourselves to those we do not love. And to those whom we love, we reveal ourselves in proportion to our love. Trinity is proof of God’s love for us because the nature of our Triune God is to Love. And this happened on the Cross where Jesus revealed the Father’s Love for us ‘in all fullness' through His Sacrificial offering of Himself. That same Spirit of the Father and of the Son, sent upon the Church at Pentecost, now reveals God’s love interiorly to us!
Hopefully today you get the sense of the ebb and flow of God who is Trinity? Just as it is God’s nature to reveal Love so we may share in eternal life, we are equally convicted to share this Love with others. This is because being caught-up in Trinitarian life will bring our love to perfection, proving our love for God and for each other. And all glory be to the Father, and to the Son, and to the Holy Spirit now and forever, Amen!