Albert Barnes writes:
Verse 3:
‘For I could wish’ … - This passage has been greatly controverted. Some have proposed to translate it, “I did wish,” as referring to a former state, when he renounced Christ, and sought to advance the interests of the nation by opposing and defying him. But to this interpretation there are insuperable objections.
(1) the object of the apostle is not to state his former feelings, but his present attachment to his countrymen, and willingness to suffer for them.
(2) the proper grammatical construction of the word used here is not I did wish, but I could desire; that is, if the thing were possible. It is not I do wish, or did wish, but I could desire ἠυχόμην ēuchomēn, implying that he was willing now to endure it; that his present love for them was so strong, that he would, if practicable, save them from the threatened ruin and apostasy.
(3) it is not true that Paul ever did wish before his conversion to be accursed by Christ, that is, by the Messiah. He opposed Jesus of Nazareth; but he did not believe that he was the Messiah. At no time would he have wished to be devoted to destruction “by the Messiah,” or “by Christ.” Nothing would have been more terrible to a Jew; and Saul of Tarsus never doubted that he was the friend of the promised Messiah, and was advancing the true interests of his cause, and defending the hopes of his nation against an impostor. The word, therefore, expresses a feeling which the apostle had, when writing this Epistle, in regard to the condition and prospects of the nation.
‘Were accursed from Chest’ - Might be anathema by Christ ἀνάθεμα εἶναι ἀπὸ τοῦ Χριστοῦ anathema einai apo tou Christou. This passage has been much controverted. The word rendered “accursed” (anathema) properly means,
(1) Anything that was set up, or “set apart,” or consecrated to the gods in the temples, as spoils of war, images, statues, etc. This is its Classical Greek meaning. It has a similar meaning among the Hebrews. It denoted what was set apart or consecrated to the service of God, as sacrifices or offerings of any kind. In this respect it is used to express the sense of the Hebrew word חרם cherem“ anything devoted to Yahweh, without the possibility of redemption.” Leviticus 27: 21; Leviticus 27: 29; Numbers 18: 14; Deuteronomy 7: 26; Joshua 6: 17-18; Joshua 7: 1; 1 Samuel 15: 21; Ezekiel 44: 29.
(2) as what was thus dedicated to Yahweh was alienated from the use of him who devoted it, and was either burnt or slain and devoted to destruction as an offering, the word came to signify a devotion of any thing to destruction, or to complete ruin. And as whatever is devoted to destruction may be said to be subject to a curse, or to be accursed, the word comes to have this signification; 1 Kings 20: 42; Isaiah 34: 5. But in none of these cases does it denote eternal death. The idea, therefore, in these places is simply, “I could be willing to be destroyed, or devoted, to death, for the sake of my countrymen.” And the apostle evidently means to say that he would be willing to suffer the bitterest evils, to forego all pleasure, to endure any privation and toil, nay, to offer his life, so that he might be wholly devoted to sufferings, as an offering, if he might be the means of benefiting and saving the nation. For a similar case, see Exodus 32: 32. This does not mean that Paul would be willing to be damned forever. For, (1) The words do not imply that, and will not bear it
(2) such a destruction could in no conceivable way benefit the Jews. (3) such a willingness is not and cannot be required. And, (4) it would be impious and absurd. No man has a right to be willing to be the “eternal enemy” of God; and no man ever yet was, or could be willing to endure everlasting torments.
‘From Christ’ - By Christ. Grotius thinks it means from the church of Christ. Others think it means “after the example of Christ;” and others, from Christ forever. But it evidently means that he was willing to be devoted by Christ; that is, to be regarded by him, and appointed by him, to suffering and death, if by that means he could save his countrymen. It was thus the highest expression of true patriotism and benevolence. It was an example for all Christians and Christian ministers. They should be willing to be devoted to pain, privation, toil, and death, if by that they could save others from ruin. My kinsmen … - My countrymen; all of whom he regarded as his kinsmen, or relations, as descended from the same ancestors. According to the flesh - By birth. They were of the same blood and parentage, though not now of the same religious belief.
Verse 4:
‘Who are Israelites’ - Descended from Israel, or Jacob; honored by having such an ancestor, and by bearing a name so distinguished as that of his descendants. It was formerly the honorable appellation of the people of God.
‘To whom pertaineth’ - To whom it belongs. It was their elevated external privilege.
‘The adoption’ - Of the nation into the family of God, or to be regarded as His special people; Deuteronomy 7: 6.
‘And the glory’ - The symbol of the divine presence that attended them from Egypt, and that finally rested over the ark in the first temple - “the Shechinah;” Exodus 13: 21-22; Exodus 25: 22.
‘And the covenants’ - The various compacts or promises which had been made from time to time with Abraham, Isaac, and Jacob, and with the nation; the pledges of the divine protection.
‘The giving of the law’ - On Mount Sinai; Psalm 147: 19.
‘And the service of God’ - The temple service; regarded by them as the pride and ornament of their nation.
‘And the promises’ - Of the Messiah; and of the spread of the true religion from them as a nation.
(From: ‘The New Testament: Notes On The Whole Bible’).
Make of this what you will!