(14-17) This life in the Spirit implies a special relation to God — that of sons. I say of sons; for when you first received the Holy Ghost it was no spirit of bondage and reign of terror to which you were admitted, but rather the closest filial relation to God. This filial relation is attested by the Divine Spirit endorsing the evidence of our own consciousness, and it includes all that such a relation would naturally include — sonship, heirship, nay, a joint-heirship in the glory of Christ, who is Himself pre-eminently the Son.
This idea of “sonship” is also worked out in the Epistle to the Galatians (Galatians 3:25; Galatians 4:1-7). It is the Christian transformation of the old theocratic idea. The Israelite, quâ Israelite, had stood in this special relation to God; now it is open to the spiritual Israel of whatever race they may be. The idea itself, too, is largely widened and deepened by the additional doctrines of the continued agency of the Spirit and of the Messiahship of Jesus. The sense of sonship is awakened and kept alive by the Spirit; and of all those in whom it is found, the Messiah Himself stands at the head, ensuring for them a share in His own glory.