Charles Ellicott Commentary Genesis 25:23

"And Jehovah said unto her, Two nations are in thy womb, And two peoples shall be separated from thy bowels. And the one people shall be stronger than the other people. And the elder shall serve the younger." — Genesis 25:23 (ASV)

And the Lord said to her.—Not by the mouth of Abraham, nor in a dream, but directly, as He spoke long ago to Adam and Eve. We read of no appearance, as in Genesis 17:1, nor must we invent one. The manner in which Jehovah thus spoke has not been revealed, and it is enough for us to know that Jehovah did speak long ago to men. The answer is in a plain form:

“Two nations are in thy womb;
And two peoples from thy bowels shall be separated;
And people shall be mightier than people;
And the great shall serve the small.”

The second line shows that even in their earliest childhood her sons would be unlike in character and unfriendly in disposition. This is followed by their development into hostile nations and the prediction that the son who started with the advantages of the birthright, the stronger physical nature, and superior strength in men and arms (Genesis 32:6), would, nevertheless, finally hold the inferior position.

There can be no doubt that the secondary cause of the vaster development of Jacob was his being placed by Joseph in the fruitful Delta, where the Israelites were constantly joined by a stream of Semitic immigrants, whose movement towards Egypt is a perfectly authenticated fact of the history of those times. (See Genesis 12:15.)