Sforno on Genesis 27:29/ספורנו על בראשית כ״ז:כ״ט

1וישתחוו לך לאומים, for even the kingdoms which will not serve you directly will be in a state of dependence on you seeing that you will be the superpower.

2הוה גביר לאחיך, seeing that Yitzchok was under the impression that he was speaking to Esau, he thought that it would be in Yaakov’s interest to endure some degree dependence upon Esau while at the same time holding on to the Land of Israel as its Abrahamitic heritage. Such a political dependence would ensure that Yaakov’s descendants would turn their attention to matters other than geo-politics, conquest, etc. The fact is, that at some time in the future the Jewish state did display expansionary tendencies, only to suffer setbacks as a result. The prophet Amos 6,8 already warned his people against such tendencies when he quotes G’d’s loathing for power politics practiced by the Kingdom of the ten tribes under the kings of Samaria. Moreover, Yitzchok thought that if Yaakov had to be subjected to foreign domination, it would be better for it to be subjected to the rule by his brother than by other nations which would treat it more cruelly. Our sages (Gittin 17) phrased this as או בטולך או בטולך דבר עשו, “it is better to be under the protection of You (G’d), or the protection of the descendants of Esau than to have to live under the rule of the Persians.” The way Yitzchok phrased his blessing was based on his knowledge that the Land of Israel would be Yaakov’s descendants exclusively, that Esau’s descendants would not have a share in it. This is why he made no mention at all of the blessing G’d gave to Avraham, nor did he make any mention of the Land of Israel.

3אוויך ארור, the word אורריך is in the plural mode seeing that there would be numerous nations or individuals who would curse the kings and ministers of Esau when they would not be granted their rightful aspirations. The Torah therefore warned the Jewish people not to curse the political leadership or the judiciary as such curses might backfire (Exodus 22,27)