Celsus, again, brings together a number of statements, which he gives as admissions on our part, but which no intelligent Christian would allow. For not one of us asserts that “God partakes of form or colour.” Nor does He even partake of “motion,” because He stands firm, and His nature is permanent, and He invites the righteous man also to do the same, saying: “But as for you, stand here by Me.” And if certain expressions indicate a kind of motion, as it were, on His part, such as this, “They heard the voice of the Lord God walking in the garden in the cool of the day,” we must understand them in this way, that it is by sinners that God is understood as moving, or as we understand the “sleep” of God, which is taken in a figurative sense, or His “anger,” or any other similar attribute.
But “God does not partake even of substance.” For He is partaken of (by others) rather than that Himself partakes of them, and He is partaken of by those who have the Spirit of God. Our Saviour, also, does not partake of righteousness; but being Himself “righteousness,” He is partaken of by the righteous. A discussion about “substance” would be protracted and difficult, and especially if it were a question whether that which is permanent and immaterial be “substance” properly so called, so that it would be found that God is beyond “substance,” communicating of His “substance,” by means of office and power, to those to whom He communicates Himself by His Word, as He does to the Word Himself; or even if He is “substance,” yet He is said be in His nature “invisible,” in these words respecting our Saviour, who is said to be “the image of the invisible God,” while from the term “invisible” it is indicated that He is “immaterial.”
It is also a question for investigation, whether the “only-begotten” and “first-born of every creature” is to be called “substance of substances,” and “idea of ideas,” and the “principle of all things,” while above all there is His Father and God.
Source: Against Celsus (New Advent)