Who is the subject (addressed in the second person) in verses 8-12? No one is named; in the second part of verse 9 “the LORD” is named, in the third person, and then the second person is resumed. Good News Translation has taken the second person to refer to the king, and so has “The king” in verse 8a (so Kirkpatrick, Briggs, Toombs, Taylor, and others; also Traduction œcuménique de la Bible, Biblia Dios Habla Hoy, New American Bible, Bible de Jérusalem, New Jerusalem Bible). Revised Standard Version‘s use of you and your makes it clear that it takes the king to be the subject. Another way of making the king the subject is to change in verse 7 from the third person to the second person vocative, “You, O king,” and keep the second person in verses 8-12 (as Biblia Dios Habla Hoy has done). New Jerusalem Bible takes the second person to refer to Yahweh (so Anderson, Weiser, Dahood, Crim). The language in places seems more appropriate of Yahweh (especially the first part of verse 9, “when you appear”); but the switch to the third person in the second part of the verse (“The LORD will swallow them up”) has been taken by some to mean that “you” in the first part of verse 9 refers to the king. Bible en français courant takes the subject in verses 8-12 to be God, who is addressed, in verse 8, “O King, you….”
Hand and right hand seem to be used synonymously; but Dahood understands them to mean “left hand” and “right hand.” Your hand in reference to the power of the king is the expression of a part for the whole. In some languages it will be possible to maintain this imagery, either as “your hand” or “his hand,” while in other languages it will be preferable and less ambiguous to follow the lead of Good News Translation. The verb find out in both lines does not mean simply to discover, but to grab, to “capture” (New International Version has “lay hold on … seize”).
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 .