We are God’s children not through nature but through grace
"The gift of sonship to God becomes ours not through being born, but through being born again."- J I Packer
Orphan Care is Gospel Reenactment. When we were on the outside without hope and home, Jesus brought us into his family (Ephesians 2:12-13, 19). What Jesus did for us is the Gospel. Today there are millions of orphans in the world without hope and home. When we give orphans hope, when we bring orphans into our families, we reenact the Gospel. - Dan Cruver
Adoption is an act of God's free grace, whereby we are received into the number, and have a right to all the privileges of, the sons of God.
Westminster Shorter Catecism Q 34
“Before orphans can enjoy the love and care of a new family, they must be legally adopted. Adoption, like justification, is simultaneously legal and relational”
-Michael Horton, Covenant and Salvation: Union with Christ, pp. 247-248
The image of “adoption” tells us that our relationship with God is based completely on a legal act by the Father. You don’t “win” a father, and you don’t “negotiate” for a parent. Adoption is a legal act on the part of the father — it is very expensive and costly only for him. There is nothing the son does to win or earn the status. It is simply received.
— Timothy Keller
Our understanding of Christianity cannot be better than our grasp of adoption. . . . If you want to judge how well a person understands Christianity, find out how much he makes of the thought of being God’s child, and having God as his Father. If this is not the thought that prompts and controls his worship and prayers and whole outlook on life, it means that he does not understand Christianity very well at all.
— J.I. Packer, Knowing God
“Extol and magnify God’s mercy, who has adopted you into his family; who, of slaves, has made you sons; of heirs of hell, heirs of the promise. Adoption is a free gift. He gave them power, or dignity, to become the sons of God. As a thread of silver runs through a whole piece of work, so free grace runs through the whole privilege of adoption. Adoption is greater mercy than Adam had in paradise; he was a son by creation, but here is a further sonship by adoption. To make us thankful, consider, in civil adoption there is some worth and excellence in the person to be adopted; but there was no worth in us, neither beauty, nor parentage, nor virtue; nothing in us to move God to bestow the prerogative of sonship upon us. We have enough in us to move God to correct us, but nothing to move him to adopt us, therefore exalt free grace; begin the work of angels here; bless him with your praises who has blessed you in making you his sons and daughters.”
Thomas Watson, A Body of Divinity, p. 240