The thought of this verse finds numerous parallels in the Psalms (see, for example, 31.23b; 37.28b).
He will guard the feet: the future tense in Revised Standard Version may be misleading if translated literally. This is not something that Yahweh will do at some future time. Rather it is his habitual behavior. New Jerusalem Bible rightly translates “He safeguards the steps of his faithful.” The word feet is here an example of a figure of speech called synecdoche, in which a part is substituted for the whole. Compare Psa 56.13. Translators may translate the Hebrew literally as in Revised Standard Version, or they may use the word “footsteps” (Revised English Bible, New American Bible) or “the steps” (New Jerusalem Bible). Others may choose not to maintain the figurative language, as in Good News Translation.
His faithful ones is singular in Hebrew. Traduction œcuménique de la Bible says “He will guard the steps of his faithful one” and indicates in a note that the “faithful one” may be a reference to the king, who is mentioned in the next verse. Most interpreters, however, understand the singular noun to be a collective noun meaning faithful ones (plural).
Be cut off: the Hebrew verb means “to be made silent,” which is a euphemism for death. In those languages that do not naturally use a passive verb form in this context, it will be necessary to say who performs this action. The context shows clearly that it is God: “he cuts off” or “he causes to perish.” In other languages it will be possible to translate simply “will die” (Contemporary English Version) or, as New American Bible says, “shall perish.”
In darkness refers to death in Sheol (see Job 10.21-22; 15.22; 17.13).
For not by might shall a man prevail: the Hebrew clause so rendered in Revised Standard Version is introduced by a word that is sometimes rendered “because.” Here it seems to introduce a kind of parenthetical statement. In fact New Jerusalem Bible places this clause in parentheses: “for human strength can win no victories.” Some other possible translations are “power is not the key to success” (New Century Version) and “We cannot win a victory by our own strength” (Contemporary English Version). See the similar thought in Psa 20.7-8a; 33.16; 147.10; and Zech 4.6.
Quoted with permission from Omanson, Roger L. and Ellington, John E. A Handbook on the First and Second Books of Samuel, Volume 1. (UBS Helps for Translators). New York: UBS, 2001. For this and other handbooks for translators see here .