ולבני הפילגשים אשר לאברהם. דרשו רז"ל פלגשם כתיב והיא קטורה שהזכיר למעלה. ונקראת פילגש לפי שהיא ממשפחת עבדים ונקראת אשה לפי שכתב לה כתובה. וכן ארז"ל נשים בכתובה פלגשים בלא כתובה, וכן כתוב בדברי הימים ובני קטורה פילגש אברהם. ומה שלא פירש הכתוב בת מי היא, יש שפירש לפי שהיתה כנענית וע"כ קצר ביחוסה כי אילו היתה פלשתית או מצרית או מאומה אחרת היה מפרש הכתוב יחוסה כמו שמצינו בעשו (בראשית כ״ח:ט׳) ויקח את מחלת בת ישמעאל בן אברהם. ומפני שהיתה מן הזרע המקולל ע"כ קצר הכתוב וסתם ולא פירש.
ולבני הפילגשים אשר לאברהם, “and to the sons of the concubines who were Abraham’s, etc.” According to Bereshit Rabbah 61,4, the word פלגשם is spelled without the letter י which indicates a plural ending, suggesting that Avraham had only one concubine ever, Hagar, and that he had remarried her after Yitzchak was married. Keturah was none other than Hagar whom we know from both Lech Lecha and Vayera. The reason she is here called פלגש, “concubine,” is only because she was descended from slaves. In 16,3 she was called אשה, “wife,” because Avraham had given her a כתובה, a financial settlement, something not given to concubines. Sanhedrin 21 explains the verse in a similar fashion. [Our versions of the Torah have פילגשים with an extra letter י, not without any letter י. Ed.]
The reason why the Torah did not tell us whose daughter Keturah was may have been that she was a Canaanite and therefore the Torah did not want to bother with her genealogy, (Nachmanides). Had she been Egyptian, or from any nation other than the Canaanites, the Torah would have given us more details about her background. We have proof of this when the Torah detailed the genealogy of the women whom Esau and Ishmael married (compare 28,9). Seeing that Keturah was a member of an accursed nation, the Torah preferred not to go into details (for the sake of Avraham?)
ואל יקשה בעיניך לאמר איך היה לוקח לעצמו אשה כנענית והוא המזהיר והמשביע את עבדו שלא יקח אשה לבנו מבנות כנען, והטעם כי אין ההקפדה רק על יצחק שהיה עקר הזרע וכענין שכתוב (בראשית כ״א:י״ב) כי ביצחק יקרא לך זרע. וכיון שנשלמה הכונה ביצחק אין להקפיד באברהם אם ישא כנענית. Do not question me how it was possible for Avraham to marry a local Canaanite woman after he had made such a point of making even his trusted servant Eliezer swear that he would not take a woman of Canaanite descent for his son Yitzchak. The prohibition never applied to anyone with the exception of Yitzchak who was predestined to carry on the line of Avraham and to be a further link in the formation of the Jewish people. Only concerning Yitzchak had G’d said: “for through Yitzchak your seed shall be known” (Genesis 21,12). Once Yitzchak was married and the stage had been set for fulfilment of the prophecy that Yitzchak would become the founding father of the Jewish people, Avraham had no reason not to marry any woman who was qualfied as suitable for him on the strength of her personal virtues.
ובמדרש קטורה זו הגר ולמה נקראת שמה קטורה לפי שהיו מעשיה נאים כקטורת. ולפי המדרש הזה יבא על נכון ויוסף אברהם לפי שהיתה שפחתו כבר בחיי שרה והוליד ממנה ישמעאל ועתה כשהחזירה אמר בה ויוסף כלשון ויוסף לדעתה. Bereshit Rabbah 61,4 which held that Keturah was none other than Hagar, the mother of Ishmael, Avraham’s other son, claims that the name Keturah reflects the concept of קטורת, incense, because her personal deeds were as pleasing to G’d as incense is to Him as a sacrificial offering. The approach reflected by this Midrash would account for the fact that this paragraph has been introduced with the words ויסף אברהם ויקח, “Avraham continued and married (remarried), etc.” After all, she had already been his servant before he had expelled her at the command of G’d and Sarah. The expression ויוסף has been used also in that sense in Genesis 35,26 when the Torah reports that Yehudah did not again sleep with Tamar after he had become aware of her true identity.