The beginning of the Gospel… the Jordan

The feast-day of Theophany, January 6, marks the day when our Lord stepped out of thirty years of obscurity to reveal Himself as the Son of God and to embark on a divine mission that would end three years later with His Crucifixion and Resurrection.

This was the starting point for all the parables, the healings and the miracles that would form the living Gospel of Jesus Christ.
Cyril of Jerusalem writes,

The beginning of the world—water,
the beginning of the Gospel—the Jordan.

When Christ came forward to be baptized in this ancient river's waters, the mysterion of the Holy Triad (το μυστηριον της αγιας τριαδος) was revealed to the world.
As the troparion for the feast teaches,

…the voice of the Father bore witness to You,
calling You His beloved Son,
and the Spirit in the form of a dove
confirmed the truthfulness
of His Word.

It's no wonder that this feast is also called the feast of Illumination (τα φωτα), for it was on this special day that mankind was enlightened by this mysterious event.

The feast day of Theophany reminds us that Christ came to take the sins of the world upon Himself. Just as He died (His immersion in the Jordan) and rose again (coming up out of the waters of the Jordan), so too we must die to our old, sinful ways and rise again cleansed, renewed and reborn. On this day, our Savior indicates the way to our salvation.