לֹֽא־יָקוּם֩ עֵ֨ד אֶחָ֜ד בְּאִ֗ישׁ לְכׇל־עָוֺן֙ וּלְכׇל־חַטָּ֔את בְּכׇל־חֵ֖טְא אֲשֶׁ֣ר יֶֽחֱטָ֑א עַל־פִּ֣י ׀ שְׁנֵ֣י עֵדִ֗ים א֛וֹ עַל־פִּ֥י שְׁלֹשָֽׁה־עֵדִ֖ים יָק֥וּם דָּבָֽר׃
A single witness may not validate against another party any guilt or blame for any offense that may be committed; a case can be valid only on the testimony of two witnesses or more.
(The above rendering comes from the RJPS translation, an adaptation of the NJPS translation. Before accounting for this rendering, I will analyze the plain sense of the Hebrew term containing אִישׁ, by employing a situation-oriented construal as outlined in this introduction, pp. 11–16.)
Prototypically, the situating noun אִישׁ profiles its referent in terms of participation in the situation under discussion. In the context of a legal proceeding (lawsuit), אִישׁ is a natural label for either of the parties, for they are constitutive of the case. In this instance, it is used to denote the accused. More precisely, it picks out “someone else” aside from the accuser, whose involvement thereby defines the situation.
Other biblical usages of singular אִישׁ to introduce an additional party as constitutive of the depicted situation (often rendered with terms like “another” or “someone else”) include: Gen 31:50; 41:38; 45:1; Exod 2:12; 12:44; 34:3; Lev 7:8; 16:21; 19:20; 20:10 (2nd instance); Num 5:13, 19; 19:9, 18; Deut 19:16; Josh 10:14; Judg 16:19; 1 Sam 2:25 (2nd instance); 10:22; 12:4; 2 Sam 17:18; 18:26 (2nd instance); 21:4; 1 Kgs 20:20; 2 Kgs 12:5 (2nd instance); Isa 3:5 (2nd instance); Ezek 1:11 (2nd instance); 18:8 (2nd instance); Ps 49:17; Prov 20:5; Est 1:8. Nearly all of these cases employ the bare noun, as here.
As for rendering into English, the NJPS “a person” misses the mark by being too general. The revised rendering represents the situation-oriented label in Hebrew with a role label (“party”), which is more idiomatic in English. (See my comment at Josh 10:24.)