But it is good to be the object of jealousy. It is hard to say whether this refers to himself or to the Galatians. Good ministers are exhorted to cherish holy jealousy in watching over the churches, "that they may present them as a chaste virgin to Christ." (2-Corinthians 11:2.) If it refers to Paul, the meaning will be: "I confess that I also am jealous of you, but with a totally different design: and I do so as much when I am absent as when I am present, because I do not seek my own advantage." But I am rather inclined to view it as referring to the Galatians, though in this case it will admit of more than one interpretation. It may mean: "They indeed attempt to withdraw your affections from me, that, when you are thrown destitute, you may go over to them; but do you, who loved me while I was present, continue to cherish the same regard for me when I am absent." But a more correct explanation is suggested by the opposite senses which the word zelousthai bears. As, in the former verse, he had used the word jealous in a bad sense, denoting an improper way of accomplishing an object, so here he uses it in a good sense, denoting a zealous imitation of the good qualities of another. By condemning improper jealousy, he now exhorts the Galatians to engage in a different sort of competition, and that, too, while he was absent.

But it is good to be, zealously affected - The meaning of this is, "Understand me: I do not speak against zeal. I have not a word to say in its disparagement. In itself, it is good; and their zeal would be good if it were in a good cause." Probably, they relied much on their zeal; perhaps they maintained, as errorists and deceivers are very apt to do, that zeal was sufficient evidence of the goodness of their cause, and that persons who are so very zealous could not possibly be bad men. How often is this plea set up by the friends of errorists and deceivers!
And not only when I am present with you - It seems to me that there is great adroitness and great delicacy of irony in this remark; and that the apostle intends to remind them as gently as possible, that it would have been as well for them to have shown their zeal in a good cause when he was absent, as well as when he was with them. The sense may be, "You were exceedingly zealous in a good cause when I was with you. You loved the truth; you loved me. Since I left you, and as soon almost as I was out of your sight, your zeal died away, and your ardent love for me was transferred to others. Allow me to remind you, that it would be well to be zealous of good when I am away, as well as when I am with you. There is not much true affection in that which dies away as soon as a man's back is turned." The doctrine is, that true zeal or love will live alike when the object is near and when it is removed; when our friends are present with us, and when they leave us; when their eye is upon us, and when it is turned away.

It is good to be zealously affected - It is well to have a determined mind and an ardent heart in reference to things which are laudable and good.
Not only when I am present - You were thus attached to me when I was among you, but now ye have lost both your reverence and affection for me. Your false teachers pretended great concern for you, that you might put all your confidence in them; they have gained their end; they have estranged you from me, and got you to renounce the Gospel, and have brought you again into your former bondage.

But [it is] good to be (s) zealously affected always in [a] good [thing], and not only when I am present with you.
(s) He sets his own true and good love, which he earnestly held for them, against the wicked vicious love of the false apostles.

But it is good to be zealously affected,.... A zealous affection when right is very commendable, as the instances of Phinehas, Elijah, John the Baptist, and our Lord Jesus Christ show, and a contrary spirit is very disagreeable. But then it must be expressed
in a good thing; in a good cause, for God, and the things of Christ; for the Gospel, and the ordinances of it, and for the discipline of God's house, and against immorality and profaneness, errors and heresies: and it should be "always"; not at certain times, and upon some particular accounts, but it should be constant, and always continue; it should be ever the same towards God, Christ, and his ministers:
and not only when I am present with you; by which the apostle suggests, that while he was with them they were zealously attached to him and truth; but no sooner was he gone from them, but their zealous affection abated, and was fixed on others, which discovered their weakness, fickleness, and inconstancy; whereas he was always the same to them, and bore the same love to them, as the following words show.

good to be zealously affected--rather, to correspond to "zealously court" in Galatians 4:18, "to be zealously courted." I do not find fault with them for zealously courting you, nor with you for being zealously courted: provided it be "in a good cause" (translate so), "it is a good thing" (1-Corinthians 9:20-23). My reason for saying the "not well" (Galatians 4:17; the Greek is the same as that for "good," and "in a good cause," in Galatians 4:28), is that their zealous courting of you is not in a good cause. The older interpreters, however, support English Version (compare Galatians 1:14).
always--Translate and arrange the words thus, "At all times, and not only when I am present with you." I do not desire that I exclusively should have the privilege of zealously courting you. Others may do so in my absence with my full approval, if only it be in a good cause, and if Christ be faithfully preached (Philippians 1:15-18).

In a good thing - In what is really worthy our zeal. True zeal is only fervent love.