6 I marvel that you are turning away so soon from Him who called you in the grace of Christ, to a different gospel,
7 which is not another; but there are some who trouble you and want to pervert the gospel of Christ.
8 But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed.
9 As we have said before, so now I say again, if anyone preaches any other gospel to you than what you have received, let him be accursed.
marvel (v.6) = surprise at the unexpected. Paul expected better of them.
turning away (v.6) = changed, altering an opinion, desertion (The tense indicates that the change is not yet complete but would continue unless …) Paul places the blame on the Galatians, not the Judaizers.
so soon (v.6) — rashly. Very little time passed between the arrival of the Judaizers and the Gentiles' perversion. Paul may have been hinting that the Judaizers found it easier to pervert them than Paul had originally found it to convert them.
Him who called you (v.6) — God
called — selected, chosen to participate in salvation by grace
The Galatians weren't being untrue to Paul, but to God who had called them.
trouble you (v.7) = disturb mentally
want to (v.7) = desire to
pervert (v.7) = transform into an opposite character (i.e. sun into darkness)
gospel of Christ (v.7) — gospel concerning Christ
Guided by Paul's usage elsewhere the words may be paraphrased, "Unto a gospel which differs so radically from that which I preached to you that it is not another gospel, for it is not a gospel at all." This was the explanation of the Judaizers, theirs was a gospel with a difference; and this the reply of the apostle, so great is the difference that what they preach is not a gospel at all. He cannot allow them even the name. He preached salvation by grace through faith, they preached salvation by law through works; the two, he asserts, are incompatible, and must be antagonistic to the end. Romans 11:6. — Galatians, by W.E. Vine, page 141.
They [the Gentiles] had been lured from the wonderful gospel of the grace of God to another gospel which had also been true, but which belonged to a former dispensation … but some zealous Jews were now perverting the good news about Christ for the Gentiles. — Studies in Galatians, by Cornelius R. Stam, page 49.
but even if (v.8) — suggesting the likelihood was very remote
we (v.8) — Paul and his traveling companions (v.2)
angel from heaven (v.8) — the highest authority imaginable (On Paul's first visit to Lystra, the Galatians thought he was a god — Acts 14:11-13.) angel = messenger.
any other gospel (v.8) — contrary to — Paul's gospel was complete and final.
accursed (v.8) — anathema, incur the disfavor of God
before/now (v.9) — referring to Paul's earlier writings, not the previous sentence
received (v.9) = appropriate to one's self, used of a hospitable welcome as a host gives to his guests.
Verse 8 says, "if, by any chance, anyone should preach …" And verse 9 says, "If, as a mater of fact, anyone is preaching …"
Verse 8 says, "gospel we preached" (emphasis on the preacher, Paul). Verse 9 says, "gospel you received" (emphasis on the hearers, the Galatians).
Paul is more stern and angry with the Galatians who had fallen away doctrinally than he was with the Corinthians who had fallen away morally.
Verse 9 applies the anathema directly to the Judaizers.
Those men from Judea who had gone to Antioch, and then to Corinth, and to Galatia to bring Gentile believers back under the law of Moses were called troublemakers, not only by Paul, but Peter also, and the great leaders of the Jerusalem council. They wrote letters to the churches: The apostles, the elders, and the brethren, To the brethren who are of the Gentiles in Antioch, Syria, and Cilicia: Greetings. Since we have heard that some who went out from us have troubled you with words, unsettling your souls, saying, “You must be circumcised and keep the law” — to whom we gave no such commandment. — Studies in Galatians, by Cornelius R. Stam, page 58.
Unto another gospel; which is not another. Paul uses two Greek words, both of which mean another, but which have a further distinct meaning of their own. The first is heteros, the second allos. Heteros means another of a different kind, allos, another of the same kind. Heteros denotes qualitative difference, allos, numerical difference. Heteros distinguishes one of two. Allos adds one besides. Every heteros is an allos, but not every allos is a heteros. Heteros involves the idea of difference of kind, while allow denotes simply distinction of individuals. Heteros sometimes refers however, not only to differences in kind but also speaks of the fact that the character of the thing is evil or bad. That is, the fact that something differs in kind from something else makes that thing to be of an evil character. We have the word heterodoxy, made up of heteros, and the word doxa, which means opinion. Paul's doctrine of grace is God's truth, and anything that differs in kind from it must necessarily be false doctrine. Heterodoxy is false doctrine.
When Paul speaks of the Galatians turning to a herteros gospel, he means that they are turning to a gospel that is false in its doctrine. It is not only different in character from the gospel which he preached to the Galatians, but it is different in a bad sense. It is essentially evil. We have here in the expression, heteros gospel, a contradiction in terms. Gospel is from euaggelion which means good news. There cannot be a herteros good news, that is, a message of good news different in kind from that which Paul preached, and different in an evil sense, and yet be a message of good news.
Then he says that it is not an allos gospel. It is not only different in kind. It is not a gospel at all. It is not another gospel even when considered in a numerical way. There can be only one message of good news. Arthur S. Way in his excellent translation of Galatians renders heteros gospel, an opposition gospel, allow gospel, an alternative gospel. Thus, the Galatians were turning to an opposition gospel diametrically opposed to Paul's message of grace, and this opposition gospel was not an alternative one. — Galatians in the Greek New Testament, by Kenneth S. Wuest, page 36-38.