Who is Ketura, and what is the significance of Avraham's marriage to her?
We read in Parashat Chayei-Sara of Avraham’s marriage after Sara’s death to a woman named Ketura (25:1). Rav Shimshon Raphael Hirsch, in his commentary, notes that Avraham’s remarriage should come as no surprise given the importance of marriage in our religious tradition:
That Abraham married again is not so surprising when we remember that he lived thirty-five years longer after Sarah’s death, more than the average length of married life nowadays. Apart from that, our sages teach that a man is not “whole” without a wife, the task of a human being is at all times too great to be able to be fully accomplished by one person alone.
Regarding the identity of Ketura, Rashi famously cites the comment of the Midrash (Bereishit Rabba 61:5) that “Ketura” is actually another name for Hagar, Sara’s Egyptian maidservant whom Avraham had married and who bore Yishmael. Avraham had sent Hagar away, together with her son, as God commanded him (21:12), and now, according to Rashi, he brought her back and remarried her. Rashi here follows the Midrashic tradition he cited earlier in his commentary (to 24:62) that Yitzchak met his bride, Rivka, when he had gone to find Hagar and bring her back to his father.
Other commentators, however, including the Rashbam, Chizkuni and Ibn Ezra, make a point of noting that according to the peshat (straightforward reading of the text), Ketura was a different woman. Ibn Ezra draws proof to his position from the fact that the Torah later (25:6) speaks of Avraham’s pilagshim (“concubines”), in the plural form, indicating that he had more than one concubine. It stands to reason, Ibn Ezra contends, that this verse refers to Hagar and Ketura, who were two separate women.
Indeed, the Midrash Tanchuma (8) attributes the theory identifying Ketura as Hagar to the minority view of Rabbi Yehuda Ha-nasi, noting that according to the majority view among the Sages, Ketura was a different woman.
This is also the view taken by the Yalkut Shimoni (Iyov 903), which adds an insightful comment into the significance of Avraham’s three marriages. The Yalkut notes that Sara, who was Avraham’s niece, descended from Noach’s son Shem, whereas Hagar, an Egyptian, originated from the line of Cham, Shem’s brother, from whom the Egyptian nation developed (see Bereishit 10:6). And Ketura, according to the Yalkut, was a descendant of the third son of Noach, Yefet.
It thus emerges that over the course of his life, Avraham married and begat children from descendants of all three families from whom all of mankind descends.
Rav Asher Brander (http://www.kehilla.org/parsha-reflections-1/chayei-sarah-5769-avraham---something-for-everyone) explains the significance of Avraham’s marriages as it emerges from the Yalkut. When God first spoke to Avraham, he promised, “ve-nivrekhu vekha kol mishpechot ha-adama” (12:3), which is generally translated as, “all families on earth will be blessed through you.” The Rashbam (28:14), however, interprets the word “ve-nivrekhu” as a reference to “grafting,” indicating that all families on earth will somehow mix and be connected with Avraham. According to the Yalkut, it seems, this blessing was fulfilled through Avraham’s marriages into all three families that descended from Noach after the deluge.
Rav Brander concludes by noting how this insight should affect the way we look upon all people, and the world in general:
It may take a few thousand years, but the notion that there is a piece of Avraham in every human being, means that hope, and pining for a connection to the Master of the Universe springs eternal...waiting to be ignited, to fulfill the words of the prophet: “For then will I turn to the nations a pure language, that they may all call on the name of the Lord – to serve him as one” (Tzefanya 3:9).