8 For there are certain heretics called Sabellians, who are also called Patripassians, who affirm that it was the Father Himself that had suffered. Do not thou so affirm, O Catholic; for if you will be a Patripassian, you will not be sane. Understand, then, that the incarnation of the Son is termed the sending of the Son; and do not believe that the Father was incarnate, but do not yet believe that He departed from the incarnate Son. The Son carried flesh, the Father was with the Son.
If the Father was in heaven, the Son on earth, how was the Father with the Son? Because both Father and Son were everywhere: for God is not in such manner in heaven as not to be on earth. Hear him who would flee from the judgment of God, and found not a way to flee by: “Whither shall I go,” says he, “from Your Spirit; and whither shall I flee from Your face? If I ascend up into heaven, You are there.” The question was about the earth; hear what follows: “If I descend unto hell, You are there.” If, then, He is said to be present even in hell, what in the universe remains where He is not present?
For the voice of God with the prophet is, “I fill heaven and earth.” Hence He is everywhere, who is confined by no place. Turn not thou away from Him, and He is with you. If you would come to Him, be not slow to love; for it is not with feet but with affections you run. You come while remaining in one place, if you believe and lovest. Wherefore He is everywhere; and if everywhere, how not also with the Son? Is it so that He is not with the Son, while, if you believe, He is even with you?
Source: Tractates on the Gospel of John (New Advent)