The first three days after Christmas Day, that is, the Second Third, and Fourth Days of Christmas, each have a major feast assigned to them. On this Third Day of Christmas we also observe the Feast of St. John the Evangelist. John was an Apostle and the brother James, both Sons of Zebedee. Along with James as well Simon Peter, he made up sort of an "inner circle" of dcisciples who among other things are recorded as witnessing the Transfiguration and whom were asked by Jesus to stay up and wait with Him in the garden on the night of his passion. John is credited with writing the Gospel of John, my favorite, along with the three Epistles of John and the Book of Revelation.
I've always appreciated the dichotomy between the Synoptic Gospels (Matthew, Mark and Luke) and the Gospel of John. The Synpotics (meaning "same eye" or "same vision" because of their similarities and use of common sources) present Jesus as a very human person. John, on the other hand, has Jesus as a majestic, serene, always-on-top-of-it figure, more God than human. And that's the point, or one of them. Jesus is, after all, both human and Divine. In fact, we get much of our divine imagery of Christ from John's Gospel, especially in the Prologue. It's no coincidence that the first three words of the Gospel, "In the beginning" are the same first three words of Genesis, after all. John explains Jesus as the pre-existing Logos, the Word of God, who comes into the world to save it. In John's gospel Jesus makes long speeches about himself and tells few parables, and in John's Gospel we get some of the most beautiful images of Jesus: the Gate, the Door, the Good Shepherd. I am drawn to the poetry and mystery and depth of the Fourth Gospel; there's a part of me that wishes we could just use the whole thing every year, rather than at Lent and Easter and a few other occasions. We need the Synoptics and John to get more complete, if always imperfect, view of Jesus the Christ.
John likes to use "light" imagery and motifs, and so it's appropriate that we observe his feast in this Season of Light.
Shed upon your Church, O Lord, the brightness of your light, that we, being illumined by the teaching of your apostle and evangelist John, may so walk in the light of your truth, that at length we may attain to the fullness of eternal life; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, for ever and ever. Amen.