“God’s Spirit doesn’t make us slaves who are afraid of him. Instead, we become his children and call him our Father. God’s Spirit makes us sure that we are his children.”
Romans 8:15-16 CEV
There is a subtle difference between slave and child.
Both obey. Both submit. Both are under that authority.
The subtle difference is fear.
A slave responds out of fear for his or her life. When a slave sees he/she has to earn the master’s favor, or make up for the debt accrued, he/she will always be a slave to fear.
The only difference is the child responds to the love of God as His Father. A love that changed how the child sees his/her place in the family. A place that can’t be earned, only accepted. That’s why a child obeys.
The Holy Spirit is God’s gift to us to show us we are accepted in the family. We have nothing to fear.