Children of God through union with Christ
Believers, being united to Christ, become children of God, and members of the family of heaven. By their union with him, who is the Son of God by nature, they become the sons of God by grace (John 1:12.)
And thus they, who are by nature children of the devil, become the children of God. They have the Spirit of adoption (Rom 8:15), namely, the Spirit of his Son, which brings them to God, as children to a Father; to pour out their complaints in his bosom, and to seek necessary supplies. ‘Because you are sons, God has sent forth the Spirit of his Son into your hearts, crying, Abba, Father.’ (Gal 4:6) Under all their weaknesses, they have fatherly pity and compassion shown them: ‘Like as a father pities his children; so the Lord pities those who fear him.’ (Psa 103:13)
They are heirs of, and shall inherit the promises (Heb. 6:12). Nay, they are heirs of God, who himself is the portion of their inheritance (Psa 16:5), ‘and joint-heirs with Christ’ (Rom 8:17). And because they are the children of the great King, and heirs of glory, they have angels for their attendants, who are ‘sent forth to minister to those who shall be heirs of salvation’ (Heb. 1:14).
Human Nature in Its Fourfold State
(Edinburgh, UK: Banner of Truth, 1964)