I've been hearing a lot about this woman named Keturah who married Abraham after Sarah died. Who is she and where was she from?
This is rashi's explanation (via the Chabad site)
And Abraham took another wife and her name was Keturah. א. וַיֹּסֶף אַבְרָהָם וַיִּקַּח אִשָּׁה וּשְׁמָהּ קְטוּרָה:
Keturah: (Gen. Rabbah 61:4) This is Hagar. She was called Keturah because her deeds were as beautiful as incense (קְטֹרֶת), and because she tied (קָטְרָה, the Aramaic for“tied”) her opening, for she was not intimate with any man from the day she separated from Abraham.
קטורה: זו הגר, ונקראת קטורה על שם שנאים מעשיה כקטרת ושקשרה פתחה שלא נזדווגה לאדם מיום שפרשה מאברהם: