In verse 126 the psalmist calls upon Yahweh to act, that is, to punish those who are not obeying the Law. Good News Translation has line a in the second person, for consistency with line b; an incautious reader of Revised Standard Version might think that in line b someone other than the LORD of line a is being addressed.
The Hebrew text begins verse 127 with a phrase ordinarily translated Therefore (Revised Standard Version), which makes for a strange connection with verse 126, since it implies that because the Law is being broken the psalmist loves it. (This Hebrew phrase begins with the letter ʿayin, just like the other lines in this strophe; matching lines may have been more important to the psalmist than making the discourse flow smoothly.) So some take the Hebrew as an affirmation: “Rightly” (New Jerusalem Bible), “Truly” (New English Bible). For the thought of this verse, see verses 14, 72.
The Hebrew text of verse 128a is hard to understand; it seems to mean “Therefore all precepts (of) all I follow.” The Hebrew “all precepts (of) all” seems to be an error for “all your instructions” (see Anderson, Briggs). The Septuagint and Jerome read “all your commandments,” which is preferred by Revised Standard Version, Good News Translation, New English Bible, New International Version, Bible de Jérusalem, New Jerusalem Bible, Biblia Dios Habla Hoy. But Hebrew Old Testament Text Project prefers the Hebrew text, saying it means “all the precepts in their totality or in every domain whatsoever, without exception.” This is how Traduction œcuménique de la Bible translates: “Thus I find all the precepts just in all points.”
There is also considerable difference of opinion over the meaning of the Hebrew verb “be straight” in this context. Revised Standard Version has I direct my steps, and Good News Translation “follow.” Holladay defines it here “keep precisely”; New American Bible has “go forward,” and New English Bible “find the right way.” New Jerusalem Bible translates “Truly by all [Your] precepts I walk straight,” and New Jerusalem Bible “I rule my life by all your precepts.” For verse 128b see 104b.
Quoted with permission from Bratcher, Robert G. and Reyburn, William D. A Handbook on the Book of Psalms. (UBS Helps for Translators). New York: UBS, 1991. For this and other handbooks for translators see here .