June 15 is Trinity Sunday, the first Sunday after Pentecost, a festival that celebrates and affirms the doctrine of the Trinity — the teaching that God is three “persons” (Father, Son, and Holy Spirit) in one.
This doctrine is not actually taught in the Bible; in fact the word “trinity” itself is not a biblical word. Rather, the doctrine arose in the early centuries of Church history, as people sought to answer the question “Who are God, Jesus, and the Holy Spirit in relation to each other?” Believe it or not, this is a question that was hotly debated in the early church, especially between the years 325 and 451. People debated about what exactly it means to say that Jesus is the “Son of God”. Likewise, people debated about the relationship between God and the Holy Spirit. Each viewpoint was supported by biblical references, and claimed to be the only correct viewpoint!
The issue was finally settled at the Council of Chalcedon in the year 451, when it was agreed that the Father, the Son, and the Holy Spirit together are God — and one God, not three Gods. This teaching is reflected in the wording of the Nicene Creed (#578 in the Book of Praise). Notice that, although the Nicene Creed is structured in the same way as the Apostles’ Creed (#539), its wording is much longer, and much more detailed and precise.
Interestingly enough, the doctrine of the Trinity became such a basic part of Christian doctrine that it was not seriously challenged during the Reformation (1517-1648), and is still accepted by Christian churches of all denominations today.
The symbolic color for Trinity Sunday is white, signifying joy and celebration.