Galatians 4:18

It is good to be zealously affected always in a good thing. — A disinterested zeal between teachers and taught is indeed good in itself. The Apostle does not wish to dissuade the Galatians from that. He would be only too glad to see such a mutual interchange himself — in his absence as well as in his presence. It seems a mistake to refer this either to the Galatians alone or to St. Paul alone. The proposition is stated in a general form, so as to cover both. It is right to be zealously affected always. Their eager zeal should not have its ebbs and flows, but should subsist constantly, whether those between whom it is felt are present together or not.

In a good thing. — This expression corresponds to “but not well” in the last verse, and means honestly, disinterestedly, with a view to the spread of the gospel, and not to personal ascendancy.