אַל־תִּתֵּן֙ אֶת־אֲמָ֣תְךָ֔ לִפְנֵ֖י בַּת־בְּלִיָּ֑עַל כִּֽי־מֵרֹ֥ב שִׂיחִ֛י וְכַעְסִ֖י דִּבַּ֥רְתִּי עַד־הֵֽנָּה׃
No tengas á tu sierva por una mujer impía: porque por la magnitud de mis congojas y de mi aflicción he hablado hasta ahora.
Siftei Chakhamim
Do not say this (לא תאמר כן)... Rashi added in the wordsתאמר כן (say this) because Yoseif had declared them as spies, so the proper word [to deny this] would be אַל. So we see with Channah (Shmuel I, 1:16). Eli thought she was a drunk, and she replied [in denial]: אַל תתן אמתך לפני בת בליעל. Whereas לא [when standing alone] is the proper reply to a question or a request.