Abraham proceeded and took a wife whose name was Keturah. She bore him Zimran and Jokshan and Medan amd Midian and Ishbak and Shuah, Jokshan begot Sheba and Dedan, and the children of Dedan were Asshurim, Letushim, and Leummim. And the children of Midian - Ephah and Epher, and Hanoch, and Abida, and Eldaah; all these were the descendants of Keturah.
The text was to be the introduction to the birth of Esav and Yaakov, according to E, which is alternative to the story of Yitzchak, who died according to E. The alternative account could obviously not be given. Instead, RJE wrote a text, to do away with the children of Avraham:Abraham gave all that he had to Isaac. But to the concubine-children who were Abraham's, Abraham gave gifts; then he sent them away from Isaac his son, while he was still alive, eastward to the land of the east.
But the account that could not be given, still had a Berachah in it which Abraham received at the end of his life. It was possible to save this dangling Berachah, and RJE did this in an ingenious way.