How does the wording of this posuk reveal what Aner, Eshkol and Mamre each counseled Avrohom concerning his circumcision?
(14,13) “And the fugitive came and told Avrom the Ivri who was dwelling in the Eilonei Mamre the Emorite, the brother of Eshkol and the brother of Aner, and they were members of the Bris of Avrom.”
The midrash (Bereishis Rabbah 42:8) brings a difference of opinion as to the meaning of “Eilonei Mamre” - R. Yehudah says that it means “the plains of Mamre”, but R. Nechmiah says that it means “the palace of Mamre”. According to R. Yehudah’s opinion the place is called Mamre, and according to R. Nechemiah’s opinion the person is called Mamre. And why was he called Mamre (ממרא)? R. Azariah in the name of R. Yehudah in the name of R. Simon says it was because he spoke brazenly (המרא פנים) to Avrohom - When Hashem told Avrohom to circumcise himself, he went and took counsel from his three friends. Aner said to him: You are already one hundred years old, and you are going to afflict yourself? Eshkol said to him: Why are you going to deliver yourself fatally into the hand of your enemies (when they hear that you are sick and weak they will come and kill you)? Mamre said to him: Your G-d Who stood by you in the fiery furnace and with the kings and with the famine, yet in this matter, when He tells you to circumcise yourself, you will not listen? Hashem said to him (Mamre): You counseledcounseled him to circumcise himself. By your life, I will not appear to Avrohom neither in the palace of Aner nor in the palace of Eshkol, but in your palace. This is why it says “and He appeared to him in Eilonei Mamre” (Bereishis 18:1).
Why did the midrash need to detail everyone’s advice? It should have simply said that Eshkol and Aner advised him not to circumcise himself, and Mamre answered him that he should circumcise himself!
Furthermore, how did the midrash know that Eshkol answered like this and Aner answered like that - maybe it was the opposite way round or maybe they both gave the same response!
But Chazal derived their explanation from a close examination of the posukim, from the Torah’s precise choice of words. Because they saw two difficulties in the language of the posuk “the brother of Eshkol and the brother of Aner”. The first problem is that the repetition of the phrase “the brother of” seems to be superfluous, since it could have simply said "the brother of Eshkol and Mamre". The second problem is that from the posuk in Bereishis 14:24 which says “Aner, Eshkol and Mamre should take their portion” it seems that Aner was older than Eshkol, because the Torah normally lists brothers in order of age. So why here did the Torah mention Eshkol before Aner?
But according to each one’s response to Avrohom that are taught in the midrash these problems are completely resolved, because the word 'brother' has other connotations apart from its primary meaning of one born from the same parent, one of which is an agreement of opinion between two people.
The response of Eshkol - “Why are you going to deliver yourself fatally into the hand of your enemies?” - did not mean that Avrohom should not circumcise himself. He meant that he should not do it publicly but in private, so that no one will know about it until he recovers and is no longer weak, and thus not be in danger from his enemies. In contrast, the answer of Aner was to completely refrain from doing the circumcision because of his frailty due to old age.
Hence the advice of Eshkol was similar to the advice of Mamre since they both agreed that Avrohom should do the circumcision. Their only difference was that Eshkol counseled to do it private because of his enemies and Mamre counseled to do it publicly to sanctify Hashem’s name. Thus Eshkol and Mamre were not only familial brothers, but brothers in the sense that they shared essentially the same view, since they both agreed that Avrohom should carry out the circumcision. Aner on the other hand who advised Avrohom to completely refrain from doing the circumcision was a brother to Mamre only in a familial sense.
For this reason the phrase “the brother of” appears together with each name and Eshkol’s name is written first, to intimate that Eshkol was more of a brother to Mamre than Aner was, because Eshkol was a brother in two ways - by birth and by his opinion, whereas Aner was Mamre’s brother only by birth. And the posuk concludes that “they were members of the Bris of Avrom”, because in the matter of the circumcision of Avrohom they all gave advice.