The house of God, which is the Church of the living God, the pillar and ground of truth

The Church, according to St. Cyril of Alexandria, is the holy city, which has not been sanctified by observing the law - for the law made nothing perfect (Heb. 7:19) - but by becoming conformed to Christ: participating in the divine nature through the communication of the Holy Spirit, who stamped us with His seal in the day of our deliverance when we were washed from every stain. 

The humanity of Christ provides the opportunity for the manifestation of the Trinity. That is why the Theophany and the Transfiguration are celebrated so solemnly: it is the revelation of the Trinity that is being celebrated: for the voice of the Father was heard and the Holy Spirit was present the first time in the form of a dove. - Vladimir Lossky, Mystical Theology of the Eastern Church

John the Baptist came preaching

For this end he exhorted them to confess and repent of their sins, not that they should punished, but that they might more easily receive the subsequent remission. For had they not condemned themselves, they could not have sought after His grace: and not seeking, they could not have obtained remission…

Because in fact the things concerning Christ had been up to that time veiled, and many thought he was dead, owing to the massacre which took place at Bethlehem. For though at twelve years old He discovered Himself, yet did He also quickly veil Himself again. And for this cause there was need of that splendid exordium and of a loftier beginning. - St. John Chrysostom, Homily

The Bible and the Holy Fathers
1 Tim. 3:14-4:5; Mt. 3:1-11
Saturday before Theophany