Genesis 25:21-23 Amplified Bible, Classic Edition (AMPC)
21 And Isaac prayed much to the Lord for his wife because she was unable to bear children; and the Lord granted his prayer, and Rebekah his wife became pregnant.
22 [Two] children struggled together within her; and she said, If it is so [that the Lord has heard our prayer], why am I like this? And she went to inquire of the Lord.
23 The Lord said to her, [The founders of] two nations are in your womb, and the separation of two peoples has begun in your body; the one people shall be stronger than the other, and the elder shall serve the younger.