This being the fact as to sin and its servitude, the Lord proceeds to deal with servitude in God's house. Servitude and its spirit are manifested in the house of the Father. The bond slave abideth not in the house forever.
So long as he is a bond slave and not emancipated from the fetters of mere race, so long as he is ruled by the servile spirit, there is no perpetuity about his relation to the Father. He can be sold away (Genesis 21:10; Galatians 4:30).
An involuntary subject of the Law, who belongs to the theocracy as a slave merely, and because he cannot help himself, and occupies a position which a slave does in the family of sin, has lost all freedom and spontaneity in his service, and will find himself cast out at last.
But the son abideth forever. Sonship is the only principle on which continuance in the house can be secured. It has been much debated whether the ὁ υἱός of the thirty-fifth verse goes beyond the idea of sonship, the generic antithesis to the idea of slave.
Certainly this seems the primary reference. In the following verse, the Son, in his loftiest functions, and as identifying himself with "the truth" of John 8:32, entirely fulfils the conception of "Sonship" and eternal abiding in the Father's house, and therefore is entrusted with the power of emancipating all slaves, of adopting sons into the Father's royal house.
Thus we may suppose that the first use of the term "son," though laying special emphasis on the spirit and conditions of sonship, yet points to him who entirely embodies, enshrines, and has from before all worlds realized the Divine idea of Son—the only begotten Son—in the bosom of the Father.