Genesis 35:22

22And when he was living in that region, Reuben went out, and he slept with Bilhah the concubine of his father, which was not such a small matter as to be hidden from him. Now the sons of Jacob were twelve.
35:22 The concubine: She was his lawful wife; but, according to the style of the Hebrews, is called concubine, because of her servile extraction.(Challoner)
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