“Therefore it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham; who is the father of us all,”
King James Version (KJV)
4:16 Therefore it - The blessing. Is of faith, that it might be of grace - That it might appear to flow from the free love of God, and that the promise might be firm, sure, and effectual, to all the spiritual seed of Abraham; not only Jews, but gentiles also, if they follow his faith.
Ro 4:16 Therefore [it is] of faith. The inheritance promised to Abraham and his seed. It comes through faith, and hence is a free gift (of grace). That [it might be] . . . sure. It could not be sure if it had to be secured by the righteousness that is of law, since none can keep the law perfectly. But all can secure it through faith. To all the seed. To all children of Abraham, whether those of the law, the Jews, or those of the faith of Abraham, who become his children by exercising his faith, whether Jew or Gentile. See Ga 3:7.