וַיֵּצֵ֨א מֹשֶׁ֜ה מֵעִ֤ם פַּרְעֹה֙ אֶת־הָעִ֔יר וַיִּפְרֹ֥שׂ כַּפָּ֖יו אֶל־יְהוָ֑ה וַֽיַּחְדְּל֤וּ הַקֹּלוֹת֙ וְהַבָּרָ֔ד וּמָטָ֖ר לֹא־נִתַּ֥ךְ אָֽרְצָה׃
И вышел Моисей из города от фараона и простер руки свои к Господу; и прекратились громы и град, и на землю не пролился дождь.
Rashi
לא נתך means [RAIN] DID NOT REACH the earth (i. e. no fresh rain came down) — that rain, too, which was alredy in the air at the moment when Moses was praying remained there and did not reach the ground. In a similar sense is “ותתך עלינו the curse and the oath” — a passage in the book of Ezra (really, Daniel 9:11) — which signifies, “the curse and the oath have reached us”. But Menachem ben Seruk classified it in the same section as, (Ezekiel 22:22) “כהתוך כסף” which has the meaning of melting (pouring forth) metal. I agree with his opinion, because in the Targum we render ויצק, (Onkelos Exodus 38:5) “And he cast (metal)”, by ואתיך, and (Onkelos Exodus 38:27) לצקת, “to cast (metal)” by לאתכא, each of these Aramaic words being of the same root as our word נתך. Therefore לא נתך ארצה would mean: rain was not poured out to the ground.
Rashbam
נתך, an expression similar to יציקה, “pouring.” We find this root on this sense in Ezekiel 22,22 כהתך כסף בתוך כור כן תותכו בתוכה, “as silver is melted (poured into for refining) in a crucible, so you shall be melted in it.”
Haamek Davar
The thunder and the hail ceased: This is the hail that had fire in it, which Pharaoh requested [to remove].