"And the older shall serve the younger."

Question

In Genesis 25:23 and 27:40 it states:

וַיֹּאמֶר יְהוָה לָהּ שְׁנֵי גיים [גוֹיִם] בְּבִטְנֵךְ וּשְׁנֵי לְאֻמִּים מִמֵּעַיִךְ יִפָּרֵדוּ וּלְאֹם מִלְאֹם יֶאֱמָץ וְרַב יַעֲבֹד צָעִיר׃

and the LORD answered her, “Two nations are in your womb, Two separate peoples shall issue from your body; One people shall be mightier than the other, And the older shall serve the younger.”

But in what way did Esav (or his descendants) ever serve Ya’akov (or Israel)?

Answer 1

According to the first pasuk, the Chizkuni understands this 'servitude' mentioned in the verse as merely pointing to the fact that Yaakov will end up being the older one by virtue of him gaining the birthright and thus being served through the honour due to him as the elder:

ורב יעבוד צעיר, “and the older will become subservient to the younger.” This is where the Torah decreed that Yaakov, though the younger, will eventually wind up as the senior one of the twins to be born. Rav Hunna (Bereishis Rabbah 63:6) is quoted as having said that it means if Yaakov merits it he will become the senior, if not, Esau will become senior to him. An alternate exegesis: the word רב does not mean: “the senior one,” but simply means “הרבה,” a great deal,” or “for a long time.” The word occurs when Esau first declined Yaakov’s gift by saying: יש לי רב, “I have lots.” (Genesis 33:9).

This understanding is shared by the Da'as Zekeinim.

Radak explains that it is not a foregone conclusion that it means that Esav will be subservient to Yaakov as the grammatical structure of the pasuk means it is unclear. In fact, in recent history the descendants of Esav have been the more powerful, it is thus a reference to a future time:

The reason we face the problem of meaning in our verse is that the future of the two peoples is not spelled out clearly, in the prophecy, seeing that history teaches that the Jewish people enjoyed distinct periods in which it was in the ascendancy, whereas over the last 1000 years plus the opposite is the case. The only part of the prophecy which is clear is that during most of history Esau was indeed subservient to Israel, hence Esau is mentioned first in this part of the verse, seeing that it is the principally active subject. Not only this, but after the arrival of the Messiah this situation will be restored with Edom/Esau serving his junior brother Israel. The word רב being applied to the older of the twins refers to his seniority at the time of birth, seeing he emerged first from Rivkah’s womb. It follows that the one who emerged last must be referred to as the צעיר, the younger one. We find another examples of the word רב or at least its plural רבים referring to chronological seniority in Job 32:9 לא רבים יחכמו, “it is not the seniors who are wise.”

A different approach is understood as far as the second verse you cite.

Ramban implies that this servitude will be demonstrated on the battlefield. He writes:

And you shall serve your brother - He would be victorious in all his battles except for those with his brother.

The Daas Zekeinim adds:

והיה כאשר תריד, “it will come to pass when you will break loose; (the most common translation, rejected by our author);” (the root רדה, meaning “to subdue) occurs again in Numbers 24:19, in Bilam’s blessings, when that prophet predicts that eventually a time will come when the descendants of Israel will subdue the descendants of Esau, and that at that time Esau’s descendants will accept Yaakov’s yoke willingly.

Also refer to the Ohr HaChaim who further supports this claim:

...even when Esau dominates the rest of the world, his dominion will not extend over Jacob (the Jewish people)...

This p'shat is also employed by the Tur Ha'Aruch

So according to these views, Esav will 'serve' Yaakov and his descendant by not dominating them and will accept the Jewish people as the senior partner. Either way, the commentaries on both verses point to a future time and that is why you have not seen them being 'served' yet.