'Slave girl' in the Bible

One day, as we were on our way to the place of prayer, a slave girl met us who claimed to be inspired and was accustomed to bring her owners large profits by telling fortunes.

For it is written that Abraham had two sons, one by the slave-girl and one by the free woman.

But we see that the child of the slave-girl was born in the common course of nature; but the child of the free woman in fulfilment of the promise.

But what says the Scripture? "Send away the slave-girl and her son, for never shall the slave-girl's son share the inheritance with the son of the free woman."

Therefore, brethren, since we are not the children of a slave-girl, but of the free woman--