“Brethren according to the Flesh.”
Paul had two classes of brethren; those who were with him the children of God in Christ; these he calls brethren in the Lord, Philip, i. 14, holy brethren, &c. The others were those who belonged to the family of Abraham. These he calls brethren after the flesh, that is, in virtue of natural descent from the same parent. Philemon he addresses as his brother, both in the flesh and in the Lord. The Bible recognizes the validity and rightness of all the constitutional principles and impulses of our nature. It therefore approves of parental and filial affection, and, as is plain from this and other passages, of peculiar love for the people of our own race and country.
Commentary Romans 9
“Nationalism, within proper limits, has the divine sanction; an imperialism that would, in the interest of one people, obliterate all lines of distinction is everywhere condemned as contrary to the divine will. Later prophecy raises its voice against the attempt at world-power, and that not only, as is sometimes assumed, because it threatens Israel, but for the far more principal reason, that the whole idea is pagan and immoral.
Now it is through maintaining the national diversities, as these express themselves in the difference of language, and are in turn upheld by this difference, that God prevents realization of the attempted scheme… [In this] was a positive intent that concerned the natural life of humanity. Under the providence of God each race or nation has a positive purpose to serve, fulfillment of which depends on relative seclusion from others.”
~ Geerhardus Vos