Galatians 4:1

My point is this--As long as the heir is under age, there is no difference between him and a slave, though he is master of the whole estate.

Galatians 4:23

But the child of the slave-woman was born in the course of nature, while the child of the free woman was born in fulfillment of a promise.

Galatians 4:29

Yet at that time the child born in the course of nature persecuted the child born by the power of the Spirit; and it is the same now.

Treasury of Scripture Knowledge

Summary

Now I say, That the heir, as long as he is a child, differeth nothing from a servant, though he be lord of all;

Bible References

That

Galatians 4:23
But the child of the slave-woman was born in the course of nature, while the child of the free woman was born in fulfillment of a promise.