The following is taken from the “Jewish Women’s Archive”…my notes will be added in capital letters to further emphasis some points.

Keturah was one of Abraham’s wives. The Rabbis describe her as a woman of virtue and for that she was worthy of being joined to that righteous one [Abraham]. The Torah mentions this marriage in Gen. 25:1, after the death of Sarah and subsequent to the wedding of Isaac and Rebekah. The Rabbis present this as a lesson in proper conduct: if a man’s wife dies, and he has grown children, he should first see that they are married before himself taking a new wife (Gen. Rabbah 60:16). This implies that the Rabbis understood that Sarah died before Abraham remarried.

THE IDENTIFICATION OF KETURAH

According to one view, Abraham remarried after the death of Sarah and had a total of three wives: Sarah,Hagar and Keturah. Another (MORE ACCEPTED) tradition identifies Keturah with Hagar, and thus Abraham married only twice. Each of these views finds Scriptural support for its position: the three-wife opinion relies on Gen. 25:1: “Abraham took another wife,” implying a third wife, in addition to the first two. This school of thought is further bolstered by the fact that this wife also had a different name (Keturah); in addition, the plural wording of Gen. 25:6 (“to Abraham’s sons by concubines”) conveys that Abraham had at least two wives in addition to Sarah.

Those who identify Keturah with Hagar have rejoinders to each of these proofs. First, the wording “another [va-yosef]” in 25:1 teaches that these marriages were in fulfillment of a divine command; the proponents of this view learn this from Isa. 8:5: “Again [va-yosef] the Lord spoke to me,” where the word appears in the context of divine revelation. Second, the wife’s new name of Keturah does not necessarily teach that this was a different woman; rather, it was a name given to Hagar in recognition of her good qualities (see below). Third, the word pilegshim (concubines) in Gen. 25:6 is spelled deficiently, without the letter yod. The intent of the Torah was thus to only a single concubine, Hagar (Gen. Rabbah 61:4).

THERE MANY OTHER PROOFS THAT HAJAR AND KATURA ARE THE SAME PERSON, ONE OF THE MAJOR ONES IS THE CLEAR SCRIPTURAL PROOF SHE CAME FROM ARABIA WHICH IS ACKNOWLEDGED AND COMMON KNOWLEDGE.  ALSO THAT BOTH HAJAR AND KETURAH ARE CALLED CONCUBINE AND WIFE, ETC.

The view that was widely accepted by the Rabbis is the one which identifies Keturah with Hagar, and it appears in various midrashim.

HER MARRIAGE

In the midrashic depiction, after Abraham divorces Hagar and sends her into the wilderness she sits by the well and cries to God: “See my shame!” Hagar’s demand for justice was accepted by God, who revealed Himself to Abraham after Sarah’s death and commanded him to take back his divorcée, Hagar-Keturah (Gen. Rabbah loc. cit.).

A different story has Isaac initiating his father’s marriage. When Isaac married Rebekah, he said to himself: I have taken a wife, while my father is without a spouse! What did he do? He went and brought him Keturah. This tradition is based on Gen. 24:62: “Isaac had just come back from the vicinity of Be’er-la-hai-ro’i”—he brought back with him Hagar, who had been at “Be’er-la-hai-ro’i,” and had also given this place its name, as is related in Gen. 16:14 (Tanhuma, Hayyei Sarah 8).

THE MEANING OF THE NAME “KETURAH”

The name Keturah lends itself to a number of Rabbinic interpretations. She was perfumed (mekuteret) with commandments and good deeds (Gen. Rabbah 61:4); she was (through her good deeds) more savory (mekuteret) than all manner of spices (Pirkei de-Rabbi Eliezer [ed. Higger], chap. 29); her deeds were as fine as incense (ketoret—Tanhuma, Hayyei Sarah 8). An additional explanation gives this word the meaning of binding or sealing (keshurah). When a person secures his valuables with his seal, they are still shut when he opens his treasury. Thus, even though Abraham sent Hagar forth and she wandered in the wilderness, when he brought her back she remained chaste and no other man had known her, for which she was known as Keturah (Gen. Rabbah 61:4).

For additional Hagar traditions in the Rabbinic literature, see Hagar.

THE CHILDREN OF KETURAH AS THE REALIZATION OF THE LORD’S BLESSING TO ABRAHAM

Gen. 26 lists the six children that Keturah bore to Abraham: Zimran, Jokshan, Medan, Midian, Ishbak and Shuah, to which themidrash applies the verse (Ps. 1:3): “and whatever he does prospers” (Gen. Rabbah 61:1). These offspring express the fulfillment of the blessing given by God to Abraham in Gen. 12:3: “and all the families of the earth shall bless themselves by you,” for three families came from Abraham: the twelve chieftains from Esau, the sixteen descendants of Keturah, and (Gen. 25:23) “two nations are in your womb” (Tanhuma [ed. Buber], Hayyei Sarah 8). The Rabbis further learn from Abraham that even if a man has children while he is young, he should still take another wife in his old age and beget further offspring (Gen. Rabbah 61:3). All of Keturah’s sons were the heads of nations (Gen. Rabbah 61:5)

SO ABRAHAM LIVED WITH HIS WIFE HAJAR OR KETURAH IN HIS LAST DAYS. HOWEVER, IN THE ISLAMIC TRADITION IT IS BELIEVED THE ABRAHAM IS BURIED BESIDE SARAH IN HEBRON.