The threefold call to trust in the LORD is addressed to Israel, to the house of Aaron, and to You who fear the LORD. The second group, house of Aaron, clearly means priests, and some conjecture that Israel stands for the lay Israelites assembled in worship, while You who fear the LORD indicates the whole group, including the proselytes who may be present. Some think that You who fear the LORD means only Gentile proselytes (so Bible en français courant “recent converts”); for fear see comments on 15.4. For trust see 13.5 and comments. House of Aaron, which Good News Translation translates “priests of God,” may have to be shifted in some languages, since “priests of God” may imply a retinue of priests that are with God. It may be possible to say, for example, “priests who serve God in the Temple.”
Line b of all three verses is He is their help and their shield; this sounds like a response sung by another group. The third person their can be misunderstood to refer to some other group, so Good News Translation uses the second person plural; Biblia Dios Habla Hoy uses the first person plural. For comments on shield see 3.3; the two words shield and help are used together, as here, in 33.20. Good News Translation has translated shield in verses 9-11 as “protects.” Translators may prefer to do the same, or to keep the term shield (provided, of course, that it is a commonly known object) and to supply the function, which is to protect or defend.
The verb trust appears in the Masoretic text as an imperative; the Septuagint, Syriac, and Jerome, however, have the indicative (so New American Bible, New English Bible), which agrees better with the third person suffix their help and their shield. Good News Translation follows the Masoretic text imperative, and in line b of every stanza it uses the second person “you” to agree with the second person of the verb in line a.
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 .