וַיָּבֹ֤א בֵית־אָבִיו֙ עׇפְרָ֔תָה וַֽיַּהֲרֹ֞ג אֶת־אֶחָ֧יו בְּנֵי־יְרֻבַּ֛עַל שִׁבְעִ֥ים אִ֖ישׁ עַל־אֶ֣בֶן אֶחָ֑ת וַיִּוָּתֵ֞ר יוֹתָ֧ם בֶּן־יְרֻבַּ֛עַל הַקָּטֹ֖ן כִּ֥י נֶחְבָּֽא׃ {ס}
Then he went to his father’s house in Ophrah and killed his brothers, the sons of Jerubbaal, seventy in succession on one stone. Only Jotham, the youngest son of Jerubbaal, survived, because he went into hiding.
(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.)
Prototypically, אִישׁ is used in sketching a situation schematically. Here, it performs its basic function of labeling the situation-defining participants.
The purpose of this phrase, as Jack Sasson notes, is “to underscore the savage efficiency of the act” (Judges 1–12, Anchor Bible, p. 380). The apposed phrase שִׁבְעִים אִישׁ עַל־אֶבֶן אֶחָת sketches out the manner of action; the noun אִישׁ contributes to an immediate grasp of that scene by construing its referents as participants (i.e., victims). Meanwhile, an inference from world knowledge is that such participation was physically possible on the same stone only if they “participated” one after the other. That is, they were executed one by one. Similarly in v. 18, below.
As for rendering into English, the NJPS ‘seventy men on one stone’ nowadays evokes an overly male nuance. (The fact that women are not in view is already evident.) Worse, it undertranslates the Hebrew phrase’s notice about the manner of the killing. The revised rendering swaps the explicit (participant) information with the implicit (manner of action) information, now evoking the victims’ participation by implication rather than directly.