Another explanation of Keturah (is): because her actions were beautiful like incense, and she bare him six sons, and they were all called according to the name of Ishmael, as it is said, "And she bare him Zimran (Gen. 25:2).
Like a woman sent away from her husband, so likewise Abraham arose and sent them away from Isaac his son, from this world and from the world to come, as it is said, "But unto the sons of the concubines, which Abraham had, Abraham gave gifts, and he sent them away from Isaac his son" (Gen. 25:6), by a deed of divorcement.