Gittin 46: 'Your Silence Is Better Than Your Speech'
3 mishnayot - on tikkun olam. 1. A man who divorces his wife because of a bad reputation, which turns out to be false - they still can't remarry. But what happens if the divorce is because of a vow? 2. A husband who divorces an aylonit - what happens when she remarries and has children with the second husband? 3. One who sells himself and his children into slavery to non-Jews, is not to be redeemed, though the Gemara softens this.