Adoption

Chapter six of Murray's Redemption Accomplished and Applied covers adoption. Below is the summarizing paragraph found at the end of the chapter.

But though the relation of Fatherhood differs, it is the same person who is the Father of the Lord Jesus Christ in the ineffable mystery of the trinity who is the Father of believers in the mystery of his adoptive grace. God the Father is not only the specific agent in the act of adoption; he also constitutes those who believe in Jesus' name his own children. Could anything disclose the marvel of adoption or certify the security of its tenure and privilege more effectively than the fact that the Father himself, on account of whom are all things and through whom are all things, who made the captain of salvation perfect through sufferings, becomes by deed of grace the Father of the many sons of whom he will bring to glory? And that is the reason why the captain of salvation himself is not ashamed to call them brethren and can exult with joy unspeakable, "Behold I and the children whom God hath given me" (Heb. 2:13).