'Slave girl' in the Bible

For the Scripture says that Abraham had two sons, one by a slave girl, the other by a free woman.

But the child of the slave girl was born in the ordinary course of nature, while the child of the free woman was born to fulfill the promise.

But what does the Scripture say? "Drive off the slave girl and her son, for the slave girl's son shall never share the inheritance with the son of the free woman."

So, brothers, we are children, not of a slave girl but of a free woman.