In line a for thy work the Masoretic text has the singular “your mighty deed”; many Hebrew manuscripts have the plural, which Good News Translation prefers, “Your mighty deeds” (parallel with the plural works in line b). There is no way of knowing for sure the exact nature of the LORD’s “mighty deeds” which the psalmist praises, whether they are those that he himself experienced (see verses 10-11), or whether they are Yahweh’s acts of salvation in Israel’s history. Line b steps up line a by making work become work of thy hands and glad become sing for joy. Therefore, to reflect this intensifying movement in line b, the two lines may be translated, for example, “O LORD I am glad because of your mighty deeds; I even sing for joy because of the wonderful things you have done” or “… even more than that, I sing for joy….”

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 .