Abba, Father.

Galatians 4:1-11
What I am saying is that as long as the heir is a child, he is no different from a slave, although he owns the whole estate. He is subject to guardians and trustees until the time set by his father.
God sent the Spirit of his Son into our hearts, the Spirit who calls out, "Abba, Father." So your are no longer a slave, but a son; and since your are  a son, God has made your also an heir.
You are observing special days and months and seasons and years. I fear for you, that somehow I have wasted my efforts on you.
Days: Jewish feast days
Why?
Paul worried Galatians observing the laws and regulation, and wasted what He has told them the faith of the Lord set them free.
Child and slave is the identity when we are under the law, to learn something in God's house. When the Spirit of Jesus came into our hears, we are no longer a slave, but a son, The heir of God.
He is my father, my Lord, my savior!
How?
Don't always be a child to learning the law, but may eat the Spiritual food and be a son of God. We call Him, "Abba, Father"