Various Discourses by the Assembled Bishops; also by Eusebius, the Writer of this History
Meantime the festival derived additional luster both from the prayers and discourses of the ministers of God, some of whom extolled the pious emperor's willing devotion to the Saviour of mankind, and dilated on the magnificence of the edifice which he had raised to his memory. Others afforded, as it were, an intellectual feast to the ears of all present, by public disquisitions on the sacred doctrines of our religion. Others interpreted passages of holy Scripture, and unfolded their hidden meaning; while such as were unequal to these efforts presented a bloodless sacrifice and mystical service to God in the prayers which they offered for general peace, for the Church of God, for the emperor himself as the instrumental cause of so many blessings, and for his pious sons. I myself too, unworthy as I was of such a privilege, pronounced various public orations in honor of this solemnity, wherein I partly explained by a written description the details of the imperial edifice, and partly endeavored to gather from the prophetic visions apt illustrations of the symbols it displayed. Thus joyfully was the festival of dedication celebrated in the thirtieth year of our emperor's reign.
Source: Life of Constantine (New Advent)