On Theophany the Trinity is Revealed!
"When John immersed Christ in the waters of the Jordan, the voice of God the Father from heaven was heard: 'This is my beloved Son, in Whom I am pleased'. In the Jordan the second Person of the Holy Trinity stood, God the Son, as the God-man, and hovering above the Son of God was the Holy Spirit in the form of a light-bearing dove. This was the Theophany. Here God publicly revealed Himself as Father, Son and Holy Spirit, as the Holy Trinity. God appeared and enlightened the universe."
- Metropolitan Amphilohije and Bishop Danilo, No Faith is More Beautiful than the Christian Faith, Sebastian Press, 2015.
This is the icon of the Feast of Holy Theophany, which depicts Christ being baptized by St. John the Forerunner when the Most Holy Trinity was revealed to the world (image sourced from: christthesavioroca.org).