A.T. Robertson Commentary Romans 8:15

"For ye received not the spirit of bondage again unto fear; but ye received the spirit of adoption, whereby we cry, Abba, Father." — Romans 8:15 (ASV)

The spirit of adoption (πνευμα υιοθεσιας). See on this term υιοθεσια, Galatians 4:5. Both Jews and Gentiles receive this "adoption" into the family of God with all its privileges. "

Whereby we cry, Abba, Father " (εν η κραζομεν Αββα ο πατηρ). See Ga 4:6 for discussion of this double use of Father as the child's privilege.