But Sunday is the day on which we all hold our common assembly, because it is the first day on which God, having wrought a change in the darkness and matter, made the world; and Jesus Christ our Saviour on the same day rose from the dead.Ante-Nicene Fathers: The Apostolic Fathers with Justin Martyr and Irenaeus, Vol. 1, Ed. A. Cleveland Coxe (Grand Rapids, MI: Eerdmans, 2001), 186.
I ought to begin with the most important point, which is that God the Creator made heaven and earth and everything in them... and demonstrate that there is nothing above him or behind him, as well as that he made everything of his own free will, uninfluenced by anyone else. He is the only God, the only Lord, the only Creator, the only Father, the only one who contains all things and who commanded everything else to come into existence. How can there be any other fullness, principle, power, or god above him, since it is necessary for God, who is the fullness of all these things, to contain them in his immensity without being himself contained by anyone?Adversus omnes haereses 2.1.1-2