Galatians 4:17,18 - Joseph Benson’s Commentary on the Old and New Testaments

They zealously affect you The Judaizing teachers who are come among you express an extraordinary regard for you; but not well Their zeal is not according to knowledge, neither have they a single eye to God's glory, and your spiritual advantage. Yea, they would exclude you From me and from the blessings of the gospel; that ye might effect Might love and esteem them. Or, as some read this clause, they would exclude us, that is, me, your spiritual father, and my fellow-labourers in the gospel, from your affection, that ye may love them ardently, as the only faithful teachers of the gospel. But it is good Καλον, comely, honourable, and commendable; to be zealously affected always in a good thing In what is really worthy of our zeal: for as the beauty and excellence of zeal is to be estimated not by the degree of it, considered in itself, but by the object to which it is directed; so too the warmth of your affection toward an object truly worthy of it, should be, at all times, equally maintained; and the same fervent zeal which you have formerly expressed, ought to be manifested by you, not only when I am present with you, but in my absence also, if you really think me to deserve your regards, and have indeed received the truth in the love of it. It may be proper to observe, that the original expression “may refer either to a good person or a good thing, and may be understood of their continuing zealous in their affection, either to himself, or to the truth which he preached; but as he had been speaking of himself in the foregoing verses, he likewise seems to have still in view the warmth of their affection to him when he was present with them; though he expresses it in a graceful way, with such a latitude as may include their zeal for his doctrine as well as for his person.” Doddridge.