Gittin 4:8

If a man divorces his wife because of congenital infertility, Rabbi Yehuda says that he may not re-marry her, but the Sages say that he may. If she married another man and had children with him, after which she demands payment of her kesubah, Rabbi Yehuda says that she is advised that it is preferable not to pursue the matter.

Gittin 4:9

If a man sells himself and his children to be servants to a non-Jew, he is not redeemed (because he’ll just do it again) but his children are redeemed after he dies. If a Jew sells his field to a non-Jew and then another Jew buys it, the buyer brings first fruits. This was an enactment made in the interest of societal benefit (to provide a disincentive to selling land in Israel to non-Jews).