2. So much for the ground of sonship. Its proof lay in the _sending forth of the Spirit of the Son_.
The mission of the Son and that of the Spirit are spoken of in vv. 3-6 in parallel terms: "God _sent forth_ His Son--_sent forth_ the Spirit of His Son," the former into the world of men, the latter "into" their individual "hearts." The second act matches the first, and crowns it. Pentecost is the sequel of the Incarnation (John ii. 21; 1 Cor. vi. 19, 20). And Pentecost is repeated in the heart of every child of God. The Apostle addresses himself to his readers' experience ("because _ye_ are sons") as in ch. iii. 3-6, and on the same point. They had "received the Spirit:" this marked them indubitably as heirs of Abraham (ch. iii. 14)--and what is more, sons of God. Had not the mystic cry, _Abba, Father_, sounded in their hearts? The filial consciousness was born within them, supernaturally inspired. When they believed in Christ, when they saw in Him the Son of God, their Redeemer, they were stirred with a new, ecstatic impulse; a Divine glow of love and joy kindled in their breasts; a voice not their own spoke to their spirit--their soul leaped forth upon their lips, crying to God, "Father, Father!" They were children of God, and knew it. "The Spirit Himself bore them witness" (Rom. viii. 15).
This sentiment was not due to their own reflection, not the mere opening of a buried spring of feeling in their nature. _God sent it_ into their hearts. The outward miracles which attended the first bestowment of this gift, showed from what source it came (ch. iii. 5). Nor did Christ personally impart the assurance. He had gone, that the Paraclete might come. Here was another Witness, sent by a second mission from the Father (John xvi. 7). His advent is signalised in clear distinction from that of the Son. He comes in the joint name of Father and of Son. Jesus called Him "the Spirit of the Father;"[114] the Apostle, "the Spirit of God's Son."
[114] Matt. x. 20; Luke xi. 13; John xiv. 16; Acts i. 4, 5.
To us He is "the Spirit of adoption," replacing the former "spirit of bondage unto fear." For by His indwelling we are "joined to the Lord" and made "one spirit" with Him, so that Christ lives in us (ch. ii. 20). And since Christ is above all things the Son, His Spirit is a spirit of sonship; those who receive Him are sons of God. Our sonship is through the Holy Spirit derived from His. Till Christ's redemption was effected, such adoption was in the nature of things impossible. This filial cry of Gentile hearts attested the entrance of a Divine life into the world. The Spirit of God's Son had become the new spirit of mankind.
_Abba_, the Syrian vocative for _father_, was a word familiar to the lips of Jesus. The instance of its use recorded in Mark xiv. 36, was but one of many such. No one had hitherto approached God as He did. His utterance of this word, expressing the attitude of His life of prayer and breathing the whole spirit of His religion, profoundly affected His disciples. So that the _Abba_ of Jesus became a watchword of His Church, being the proper name of the God and Father of our Lord Jesus Christ. Gentile believers pronounced it, conscious that in doing so they were joined in spirit to the Lord who said, "My Father, and your Father!" Greek-speaking Christians supplemented it by their own equivalent, as we by the English _Father_. This precious vocable is carried down the ages and round the whole world in the mother-tongue of Jesus, a memorial of the hour when through Him men learned to call God Father.
"Because ye are sons, God sent forth the Spirit," with this cry. The witness of sonship follows on the adoption, and seals it. The child is born, then cries; the cry is the evidence of life. But this is not the first office of the Holy Spirit to the regenerate soul. Many a silent impulse has He given, frequent and long continued may have been His visitations, before His presence reveals itself audibly. From the first the new life of grace is implanted by His influence. "That which is _born of the Spirit_, is spirit." "He dwelleth with you, and _is in you_,"[115] said Jesus to His disciples, before the Pentecostal effusion. Important and decisive as the witness of the Holy Spirit to our sonship is, we must not limit His operation to this event. Deeply has He wrought already on the soul in which His work reaches this issue; and when it is reached, He has still much to bestow, much to accomplish in us. All truth, all holiness, all comfort are His; and into these He leads the children of God. Living by the Spirit, in Him we proceed to walk (ch. v. 25).