Romans 9:6

But it is not as though (ouc oion de oti). Supply estin after ouc: "But it is not such as that," an old idiom, here alone in N.T. Hath come to nought (ekpeptwken). Perfect active indicative of ekpiptw, old verb, to fall out. For they are not all Israel, which are of Israel (ou gar pante oi ex Israhl outoi Israhl). "For not all those out of Israel (the literal Jewish nation), these are Israel (the spiritual Israel)." This startling paradox is not a new idea with Paul. He had already shown ( Galatians 3:7-9 ) that those of faith are the true sons of Abraham. He has amplified that idea also in Romans 4:1 ff. So he is not making a clever dodge here to escape a difficulty. He now shows how this was the original purpose of God to include only those who believed. Seed of Abraham (sperma Abraam). Physical descent here, but spiritual seed by promise in verse Romans 8 . He quotes Genesis 21:12 .