King James Version
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.New International Version
In other words, it is not the natural children who are God's children, but it is the children of the promise who are regarded as Abraham's offspring.Catholic Public Domain Version
In other words, those who are the sons of God are not those who are sons of the flesh, but those who are sons of the Promise; these are considered to be the offspring