"And Jacob said, Sell me, as of this day" (Genesis 25:31). He said to him, "Sell me one day of your own." Rabbi Aha said: whoever knows how to reckon how many years our father Jacob dwelt in tranquility will find that Jacob dwelt in tranquility in the shadow of Esau but a single day. "And Esau said, Behold, I am going to die" (Genesis 25:32). He began to revile and blaspheme. It is not written here, "Why do I [need it]?" but rather, "Why then [lammah zeh] do I have a birthright?" [the demonstrative "this" mocking, as if pointing scornfully at sacred things].
Jacob's Single Day of Peace in the Shadow of Esau
Yalkut Shimoni on Torah 111:3
וַיֹּאמֶר יַעֲקֹב מִכְרָה כַיּוֹם, אָמַר לוֹ זַבִּין לִי חַד יוֹם מִן דִידָךְ, אָמַר רַבִּי אַחָא, כָּל מִי שֶׁיּוֹדֵעַ לְחַשֵּׁב כַּמָּה שָׁנִים יָשַׁב אָבִינוּ יַעֲקֹב בְּשַׁלְוָה יִמְצָא שֶׁיּוֹם אֶחָד יָשַׁב יַעֲקֹב בְּשַׁלְוָה בְּצִלּוֹ שֶׁל עֵשָׂו. וַיֹּאמֶר עֵשָׂו הִנֵּה אָנֹכִי הוֹלֵךְ לָמוּת, מַתְחִיל מְחָרֵף וּמְגַדֵּף לָמָּה לִי אֵין כְּתִיב כָּאן, אֶלָּא לָמָּה זֶּה לִי.