The belief in one God in three divine persons, the Father, the Son, and the Holy is unique to Christian faith but as so defined (re: nature and relations, etc) was reached only in the 4th and 5th centuries AD. It must be understood that the unity of nature does not appear as a problem in NT and indeed could only rise when a philosophical investigation of the term nature as applied to God was begun.
What we have from the Scriptures are citations like mentioning the three in the same context, e.g. in the baptismal formula of Mt 28:19, (cf also 1 Cor 12:4-6; Eph 4:4-6; 1 Pt 1:2); and the “apostolic blessing” and considered earliest formula known in 2 Cor 13:13, where Christ stands at the center as the immediate source of grace (Rom 16:20; 1 Cor 16:23), and the love of God that brought about the mission of Christ and is the ultimate source of all gifts, including the Spirit who binds the community in fellowship with one another and the community with the trinitarian community: “the grace of the Lord Jesus Christ and the love of God and the fellowship of the Holy Spirit be with all of you”. This is the opening greeting at the beginning of every Eucharistic celebration.
What the Trinity is all about we may not totally comprehend. But living the “Trinitarian life” we can try to emulate. Remember that from baptism we receive the in-dwelling of the three divine persons. They live in us, but do we live in them? How? With God the Father whose love brought about the mission of Christ for our salvation (John 3:16), ‘knowing what we need even before we ask Him’ (Lk 12:22, 39-31), we should live daily in complete trust in his fatherly providence. With Jesus whose coming and total self-giving brought us life (John 15:13), life to the full, we should follow his humble life of service and self-donation to others. With the Holy Spirit who was promised by the Son and sent by the Father in his name who will teach us everything (John 14:26), we should listen continually to the Spirit especially for its guidance and direction so that we can learn God’s will for us and be able to accomplish it making us truly the adopted children of God our loving Father! And as the economy of salvation has revealed to us the different roles of the three divine persons yet remain one God, may each one of us help build the one body of Christ which we constitute by sharing the unique gifts each one of us has received. Amen.
