Ante-Nicene Fathers, Vol IX:
Epistle to Gregory and Origen's Commentary on the Gospel of John.: Chapter XXXII

32.  Christ as Son.

None of these testimonies, however, sets forth distinctly the Saviour’s exalted birth; but when the words are addressed to Him, “Thou art My Son, this day have I begotten Thee,” 4608 this is spoken to Him by God, with whom all time is to-day, for there is no evening with God, as I consider, and there is no morning, nothing but time that stretches out, along with His unbeginning and unseen life.  The day is to-day with Him in which the Son was begotten, and thus the beginning of His birth is not found, as neither is the day of it.

Footnotes

Mark 1:11, Ps. 2:7, Heb. 1:5.