Again, not understanding the meaning of the words, “And God ended on the sixth day His works which He had made, and ceased on the seventh day from all His works which He had made: and God blessed the seventh day, and hallowed it, because on it He had ceased from all His works which He had begun to make;” and imagining the expression, “He ceased on the seventh day,” to be the same as this, “He rested on the seventh day,” he makes the remark: “After this, indeed, he is weary, like a very bad workman, who stands in need of rest to refresh himself!”
For he knows nothing of the day of the Sabbath and rest of God, which follows the completion of the world's creation, and which lasts during the duration of the world, and in which all those will keep festival with God who have done all their works in their six days, and who, because they have omitted none of their duties, will ascend to the contemplation (of celestial things), and to the assembly of righteous and blessed beings. In the next place, as if either the Scriptures made such a statement, or as if we ourselves so spoke of God as having rested from fatigue, he continues: “It is not in keeping with the fitness of things that the first God should feel fatigue, or work with His hands, or give forth commands.”
Celsus says, that it is not in keeping with the fitness of things that the first God should feel fatigue. Now we would say that neither does God the Word feel fatigue, nor any of those beings who belong to a better and diviner order of things, because the sensation of fatigue is peculiar to those who are in the body. You can examine whether this is true of those who possess a body of any kind, or of those who have an earthly body, or one a little better than this. But “neither is it consistent with the fitness of things that the first God should work with His own hands.”
If you understand the words “work with His own hands” literally, then neither are they applicable to the second God, nor to any other being partaking of divinity. But suppose that they are spoken in an improper and figurative sense, so that we may translate the following expressions, “And the firmament shows forth His handywork,” and “the heavens are the work of Your hands,” and any other similar phrases, in a figurative manner, so far as respects the “hands” and “limbs” of Deity, where is the absurdity in the words, “God thus working with His own hands?”
And as there is no absurdity in God thus working, so neither is there in His issuing “commands;” so that what is done at His bidding should be beautiful and praiseworthy, because it was God who commanded it to be performed.
Source: Against Celsus (New Advent)