That being justified by his grace - Not by our own works, but by his favor or mercy; see the notes at Romans 3:24.
We should be made heirs - See the notes at Romans 8:15, Romans 8:17.
According to the hope of eternal life - In reference to the hope of eternal life; that is, we have that hope in virtue of our being adopted with the family of God, and being made heirs. He has received us as his children, and permits us to hope that we shall live with him forever.