But then, when you knew not God, you did service unto them which by nature are no gods.
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Augustine of Hippo
AD 430
When, however, he says, “you were in servitude to those who are by nature no gods,” he sufficiently proves that one true God is God by nature, by whose name the triune God is received in the most faithful and catholic bosom of the heart. “Those who are by nature no gods” are described by him as governors and overseers. There is no creature, whether it abides in truth by giving glory to God or fails to abide in truth by seeking its own glory—there is, I say, no creature that does not willynilly serve divine providence…. But, just as the magistrate under the imperial law does nothing but what is permitted to him, so the governors and overseers of this world do nothing but whatever God allows.
Not to know God is not to know Christ, for God is known through Christ. But now, since Christ has appeared, who has taught me and has revealed God through himself—both himself as God and the Father through himself—it is no longer permitted not to know God. .
You served them, who by nature are no gods. These words are to be understood of the converts, who had been Gentiles.
Known of God. That is, approved and loved by him. (Witham)
The language of the apostle in this verse is not perhaps strictly precise. The Galatians, whom he addresses, had been converted from paganism, and of course were never subject to the law of Moses. But the apostle, by these words, entreats them not to begin now to serve these weak and useless elements, (as he calls the Jewish rites) or by this expression he may mean (as St. Chrysostom and Theophylactus explain it) the tyranny of error and wickedness. (Calmet)
And "those which are not gods".
And the Apostle Paul also, saying, "For though ye have served them which are no gods; ye now know God, or rather, are known of God"
Here turning to the Gentile believers he says that it is an idolatry, this rigid observance of days, and now incurs a severe punishment. To enforce this, and inspire them with a deeper anxiety, he calls the elements not by nature Gods. And his meaning is—Then indeed, as being benighted and bewildered, you lay grovelling upon the earth, but now that you have known God or rather are known of Him, how great and bitter will be the chastisement you draw upon you, if, after such a treatment, you relapse into the same disease. It was not by your own pains that you found out God, but while you continued in error, He drew you to Himself. He says weak and beggarly rudiments, in that they avail nothing towards the good things held out to us.
For the Jews say, that from the beginning God sanctified the seventh day, by resting on it from all His works which He made; and that thence it was, likewise, that Moses said to the People: "Remember the day of the sabbaths, to sanctify it: every servile work ye shall not do therein, except what pertaineth unto life.".
He did not therefore seek, by any depreciation of the mundane elements, to turn them away from their god, although, when he said just before, "Howbeit, then, ye serve them which by nature are no gods"