By your sword you shall live: this reference is to Esau and to his descendants, the Edomites. To live By your sword means to live by war, plunder, robbery. In many languages the sword is unknown. Even where we may translate “You will live by means of your long knife,” the sense may be far from clear. Therefore, to make this figurative expression understandable, we may need to say, for example, “You will earn your living by making war,” “You will spend your life as one who kills and robs people,” or “You will live by taking plunder.”

And you shall serve your brother: the thought behind this line is that the Edomites were to be subjected to Israel. However, it is necessary to retain here the subjection of Esau to his brother Jacob. Serve translates the same word used in verse 29. See there for suggestions. Your brother refers to Jacob, who is the younger brother, or younger twin.

But when you break loose: the verb translated break loose has no accompanying footnote in Revised Standard Version. Good News Translation, however, has “rebel; or grow restless.” The sense of the Hebrew verb is uncertain. The meaning “restless” or “unsettled” comes from a similar verb in Arabic. Driver calls attention to Edom’s revolt from Judah in 2 Kgs 8.20-22. Isaac is speaking of Esau’s descendants. We may translate the verb by such expressions as “rebel,” “break away,” “revolt,” “show signs of revolting.”

You shall break his yoke from your neck: a yoke is a wooden bar or frame placed on the necks of work animals, either one animal alone or two joined together; ropes or chains were then connected from the yoke to whatever load the animal was to pull. Frequently a double yoke joined two animals together in order to pull more effectively. The yoke is a common symbol for being in subjection or under someone’s control, as in Lev 26.13; Num 19.2. To break his yoke is to be free from the brother’s power and authority. In languages in which the yoke is unknown or cannot be used in this figurative sense, it is best to switch to a nonfigurative expression; for example, “You shall be free from him,” “You shall not longer be under his control,” or “He will no longer be the boss over you.”

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .