Now we, brethren - We who are Christians.
Are the children of the promise - We so far resemble Isaac, that there are great and precious promises made to us. We are not in the condition of Ishmael, to whom no promise was made.
Related Commentaries of Galatians 4:28
Galatians 4:28
28 Now we, brethren, as Isaac was, are the children of promise.