וְעַל־חַרְבְּךָ֣ תִֽחְיֶ֔ה וְאֶת־אָחִ֖יךָ תַּעֲבֹ֑ד וְהָיָה֙ כַּאֲשֶׁ֣ר תָּרִ֔יד וּפָרַקְתָּ֥ עֻלּ֖וֹ מֵעַ֥ל צַוָּארֶֽךָ׃
Dengan pedangmu engkau akan hidup, dan engkau akan melayani adikmu. Tetapi kelak, apabila engkau merasa dirugikan, engkau akan mematahkan kuknya dari lehermu.”
Rashi
ועל חרבך—The phrase is equivalent to בחרבך BY THY SWORD. The word על is sometimes used instead of the prefix ב, as (Ezekiel 33:26) “Ye stand by your sword (על חרבכם)”, which is the same as בחרבכם; (Exodus 6:26) “by their hosts (על צבאותם), which is the same as בצבאותם.
Chizkuni
ועל חרבך תחיה, “you will live by grace of your sword.” Yitzchok promises Esau that as a reward for having hunted deer in order to bring him delectable food, he will also henceforth be able to survive by his sword in his dangerous vocation. [The word “sword” here is used by Yitzchok as a general term for instruments used to kill, seeing that Esau had hunted for him with bow and arrow. Ed.]
Da'at Zekenim
והיה כאשר תריד, “it will come to pass when you will break loose; (the most common translation, rejected by our author);” (the root רדה, meaning “to subdue) occurs again in Numbers 24,19, in Bileam’s blessings, when that prophet predicts that eventually a time will come when the descendants of Israel will subdue the descendants of Esau, and that at that time Esau’s descendants will accept Yaakov’s yoke willingly.