Genesis 25:6

“But unto the sons of the concubines which Abraham had, etc.] These were Hagar and Keturah, though they are both called his wives, (<011603>Genesis 16:3 25:1); yet they were concubines; so Keturah, (<130132>1 Chronicles 1:32); they were, as some render the word, “concubine wives” f1372 ; they were half wives or secondary ones: the Jewish writers say that they were espoused, but not by writing, as wives were; they were under the lawful wife, when there were any, and a kind of head servants in the family, and their children did not inherit; now the sons of the concubines of Abraham were Ishmael by Hagar, and the six above mentioned by Keturah: to these Abraham gave gifts; money, gold and…”