לרפואת אבי מורי שיחי' ור' מרדכי דוד בן קריינא בתוך שח"י
אַבְרָהָם יָגֵל. יִצְחָק יְרַנֵּן.
Abraham exults, Yitzchak sings joyously,
יַעֲקֹב וּבָנָיו יָנֽוּחוּ בוֹ.
Jacob and his sons rest thereon—
Why are Avraham and Yitzchak not resting and only Yaakov is??
Also, what are the Avos doing in the middle bracha of Shmoneh Esrei? They belong in the first bracha!!?
Hashem promised Avraham lands of 10 nations but only gave us seven. In the future, He will also give us the lands of the קיני קניזי and קדמוני. In the meantime, these lands were give to Lot through Avraham and to Esav through Yitzchak [see Rashi Breishsis 15-19]. Only Yaakov gives his inheritance to the Jewish people only.
Mincha is the time of "אתה אחד ושמך אחד" - The Oneness and unity of Hashem. This will happen at the end of days when all ten lands are given over to the Jewish people. In the meantime, we have the חשבון of Lot and Esav who are holding on to the three remaining lands promised to Avraham Avinu that have not yet been given.
So at this time of אתה אחד ושמך אחד, Avraham and Yitzchak can't rest yet b/c they passed lands on to Lot and Esav which is holding back the Geulah in the meantime. But Yaakov can rest b/c he has no חשבונות with anyone. He gave over the lands to the 12 shvatim so as far as he is concerned, the Geulah can already come. Nothing is stopping it.
אברהם יגל יצחק ירנן
יעקב ובניו ינוחו בו
[עפ"י תורת מרן ראש הישיבה זצ"ל]