That is, They which are the children of the flesh, these are not the children of God…
The word "accursed" often signifies no more than being devoted to temporal death, or being made a sacrifice of (Deuteronomy 21:23, of. Galatians 3:16), and the words "from Christ" may signify" after Christ," i.e., after His example (2 Timothy 1:3). The verse then would read thus: "I could be content, nay, I should rejoice to be made a sacrifice myself, as Christ has been before me, for my brethren."
(D. Waterland, D.D.)
Parallel VersesKJV: That is, They which are the children of the flesh, these are not the children of God: but the children of the promise are counted for the seed.