Adam Clarke on Galatians 4:3

Even so we - The whole Jewish people were in a state of nonage while under the law.

The elements of the world - A mere Jewish phrase, יסודי עולם הזה yesodey olam hazzeh, "the principles of this world;" that is, the rudiments or principles of the Jewish religion. The apostle intimates that the law was not the science of salvation, it was only the elements or alphabet of it; and in the Gospel this alphabet is composed into a most glorious system of Divine knowledge: but as the alphabet is nothing of itself, unless compounded into syllables, words, sentences, and discourses; so the law, taken by itself, gives no salvation; it contains indeed the outlines of the Gospel, but it is the Gospel alone that fills up these outlines.