וַיִּשְׁלַ֧ח יְהֹוָ֛ה אִ֥ישׁ נָבִ֖יא אֶל־בְּנֵ֣י יִשְׂרָאֵ֑ל וַיֹּ֨אמֶר לָהֶ֜ם כֹּה־אָמַ֥ר יְהֹוָ֣ה ׀ אֱלֹהֵ֣י יִשְׂרָאֵ֗ל אָנֹכִ֞י הֶעֱלֵ֤יתִי אֶתְכֶם֙ מִמִּצְרַ֔יִם וָאֹצִ֥יא אֶתְכֶ֖ם מִבֵּ֥ית עֲבָדִֽים׃
GOD sent a certain prophet to the Israelites. He said to them, “Thus said the ETERNAL, the God of Israel: I brought you up out of Egypt and freed you from the house of bondage.
(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.)
In the pair of clauses וַיִּשְׁלַח ... אִישׁ נָבִיא ... וַיֹּאמֶר, the noun אִישׁ signals the discourse significance of this newly introduced participant: this is the first prophet actually sent by God since Moses; his advent creates an unusual and unexpected situation. This noun label is how speakers most efficiently enable their audience to grasp a new situation. Thus Deborah was described as אִשָּׁה נְבִיאָה—the equivalent expression for a woman—upon her introduction in Judg 4:4. (In contrast, אִישׁ is not needed to establish the reference to a person in a situation where sending messengers is taken as a given, as in 2 Chr 25:15, וַיִּשְׁלַח אֵלָיו נָבִיא.)
Because the reference is a specific one, the use of אִישׁ signals that this figure is gendered as non-womanly.
As for rendering into English, the NJPS ‘sent a prophet ... who said’ obscures his gender, which in English tends to be specified upon the introduction of a specific individual. Furthermore, it does not convey the discourse significance of this participant.
The new rendering brings more attention to this figure’s essential role, by inserting the word certain, and by breaking the sentence into shorter pieces. The latter move also admits a subject pronoun, which then gives the expected gender signal. (Similarly NLT, OJPS, NRSV, ESV.)