Incense, the wife of Abraham, whom he married probably after Sarah’s death (Gen. 25:1-6), by whom he had six sons, whom he sent away into the east country. Her nationality is unknown. She is styled “Abraham’s concubine” (1 Chr. 1:32). Through the offshoots of the Keturah line Abraham became the “father of many nations.”
Keturah
After Sarah died, Abraham married again. “Then again Abraham took a wife, and her name was Keturah.” The verses that follow give a list of sons, and one of them, Midian, becomes the father of a people who appear later in the story, including in the days of Moses. Genesis 25 does not tell us much about Keturah herself. It simply shows that Abraham’s family grew well beyond Isaac, and that his blessing was passed to Isaac while gifts went to the other sons. Read Genesis 25:1-6, and 1 Chronicles 1 repeats the names.
5 verses
Genesis
Then again Abraham took a wife, and her name was Keturah.
And she bare him Zimran, and Jokshan, and Medan, and Midian, and Ishbak, and Shuah.
And Jokshan begat Sheba, and Dedan. And the sons of Dedan were Asshurim, and Letushim, and Leummim.
And the sons of Midian; Ephah, and Epher, and Hanoch, and Abida, and Eldaah. All these were the children of Keturah.
1 Chronicles
Now the sons of Keturah, Abraham's concubine: she bare Zimran, and Jokshan, and Medan, and Midian, and Ishbak, and Shuah. And the sons of Jokshan; Sheba, and Dedan.
From Easton's Bible Dictionary
Matthew George Easton, 1897