Thus says the Lord, Behold, I will raise up evil against you out of your own house; and I will take your wives before your eyes and give them to your neighbor, and he shall lie with your wives in the sight of this sun.
When Israel dwelt there, Reuben [his eldest son] went and lay with Bilhah his father's concubine; and Israel heard about it. Now Jacob's sons were twelve.
But to the sons of his concubines [Hagar and Keturah] Abraham gave gifts, and while he was still living he sent them to the east country, away from Isaac his son [of promise].
Therefore she said to Abraham, Cast out this bondwoman and her son, for the son of this bondwoman shall not be an heir with my son Isaac. [Gal. 4:28-31.]
And Sarai said to Abram, See here, the Lord has restrained me from bearing [children]. I am asking you to have intercourse with my maid; it may be that I can obtain children by her. And Abram listened to and heeded what Sarai said.