וַיֹּ֩אמֶר֩ ל֨וֹ אֱלֹהִ֜ים אֲנִ֨י אֵ֤ל שַׁדַּי֙ פְּרֵ֣ה וּרְבֵ֔ה גּ֛וֹי וּקְהַ֥ל גּוֹיִ֖ם יִהְיֶ֣ה מִמֶּ֑ךָּ וּמְלָכִ֖ים מֵחֲלָצֶ֥יךָ יֵצֵֽאוּ׃ וְאֶת־הָאָ֗רֶץ אֲשֶׁ֥ר נָתַ֛תִּי לְאַבְרָהָ֥ם וּלְיִצְחָ֖ק לְךָ֣ אֶתְּנֶ֑נָּה וּֽלְזַרְעֲךָ֥ אַחֲרֶ֖יךָ אֶתֵּ֥ן אֶת־הָאָֽרֶץ [בראשית ל"ה:י"א י"ב]
God said to him, "I am El Shaddai. Be fruitful and multiply. A nation and an assembly of nations will come from you; and kings will go forth from your loins. And the land which I gave to Avraham and Yitzchak, I will give to you, and to your descendants after you I will give the land."
"גוי וקהל גוים - דבר אחר: שעתידים בניו להקריב בשעת אסור במות כגויים, בימי אליהו.״
A nation and an assembly of nations - This means that his sons are destined to offer up sacrifices at the time of the prohibition of the high places just as the gentile nations [did], in the days of Eliyahu. — [Old Rashi manuscript from Gen. Rabbah 82:5]
Why does Hashem insert the prophecy that Yaakov's son's will bring korbanos when במות are forbidden as part of the promise of Eretz Yisrael to Yaakov? How is it relevant??
How The Story Of Eliyahu's Forbidden Sacrifice Made It Into The Promise Of Eretz Yisrael To Yaakov