NET

16 For this reason it is by faith so that it may be by grace, with the result that the promise may be certain to all the descendants—not only to those who are under the law, but also to those who have the faith of Abraham, who is the father of us all

Darby

16 Therefore [it is] on the principle of faith, that [it might be] according to grace, in order to the promise being sure to all the seed, not to that only which [is] of the law, but to that also which [is] of Abraham's faith, who is father of us all,

KJV

16 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,