The writer of Hebrews uses these verses to make a couple of very important points. The first is that God’s discipline is an act of love. That’s hard for us to grasp. Maybe you’ve heard a child respond to their parent’s discipline with the words, “you don’t love me!” As a parent, nothing is further from the truth. Parents discipline their children because they do love them. God’s discipline is to be considered as a sign of his affection for our lives. Love motivates God’s discipline, and love governs God’s discipline. Every expression of discipline passes through the Father’s loving heart.
The second point the writer makes in this section is that discipline is based on our existing relationship with God. A father who doesn’t discipline is being negligent. A child who escapes discipline loses out of the benefits of being related to the father. But here’s the surprise: The absence of discipline informs the relational status of the person. Discipline is so much a part of God’s way with his children that if it’s absent their status as children of God should be called into question. (On the flip side we could say that discipline is a mark of assurance of salvation.) God’s discipline proves our legitimacy as children of God. Discipline is the Lord’s acknowledgement that he claims us.