Galatians 4(New Living Translation)
1 Think of it this way. If a father dies and leaves an inheritance for his young children, those children are not much better off than slaves until they grow up, even though they actually own everything their father had. 2 They have to obey their guardians until they reach whatever age their father set. 3 And that’s the way it was with us before Christ came. We were like children; we were slaves to the basic spiritual principles[a] of this world.
4 But when the right time came, God sent his Son, born of a woman, subject to the law. 5 God sent him to buy freedom for us who were slaves to the law, so that he could adopt us as his very own children.[b] 6 And because we[c] are his children, God has sent the Spirit of his Son into our hearts, prompting us to call out, “Abba, Father.”[d] 7 Now you are no longer a slave but God’s own child.[e] And since you are his child, God has made you his heir.
In simple terms, a baby/child cannot claim his inheritance given by the father until he/she reaches a certain age (maturity). Meanwhile his inheritance is protected by law until he grows up to that age. Once he has reached the age of maturity(appointed time), the law no longer applies and he/she is then entitled to his/her inheritance.
What it means is that a person cannot be heir to the inheritance of the Father if he is still under the law. He has to get out of that law to claim his inheritance and it can only be done when Jesus comes into his life.
So, have you ever seen an adult becoming a child again? Yes. Well it is for those who have been bought by the precious blood of Jesus who have decided to go back to the law. When a person goes back to fellowship with the law, he is actually surrendering his inheritance/birthright; then he wonders why he is not able to receive fully the promises of God.
When a christian decides to live under law he will not mature spiritually because he has decided to move from adulthood to babyhood. The only way to mature and be successful in our christian walk is to enter into His finished work on the cross.