(ח) וַיָּבֹ֖א עֲמָלֵ֑ק וַיִּלָּ֥חֶם עִם־יִשְׂרָאֵ֖ל בִּרְפִידִֽם׃ (ט) וַיֹּ֨אמֶר מֹשֶׁ֤ה אֶל־יְהוֹשֻׁ֙עַ֙ בְּחַר־לָ֣נוּ אֲנָשִׁ֔ים וְצֵ֖א הִלָּחֵ֣ם בַּעֲמָלֵ֑ק מָחָ֗ר אָנֹכִ֤י נִצָּב֙ עַל־רֹ֣אשׁ הַגִּבְעָ֔ה וּמַטֵּ֥ה הָאֱלֹקִ֖ים בְּיָדִֽי׃ (י) וַיַּ֣עַשׂ יְהוֹשֻׁ֗עַ כַּאֲשֶׁ֤ר אָֽמַר־לוֹ֙ מֹשֶׁ֔ה לְהִלָּחֵ֖ם בַּעֲמָלֵ֑ק וּמֹשֶׁה֙ אַהֲרֹ֣ן וְח֔וּר עָל֖וּ רֹ֥אשׁ הַגִּבְעָֽה׃ (יא) וְהָיָ֗ה כַּאֲשֶׁ֨ר יָרִ֥ים מֹשֶׁ֛ה יָד֖וֹ וְגָבַ֣ר יִשְׂרָאֵ֑ל וְכַאֲשֶׁ֥ר יָנִ֛יחַ יָד֖וֹ וְגָבַ֥ר עֲמָלֵֽק׃ (יב) וִידֵ֤י מֹשֶׁה֙ כְּבֵדִ֔ים וַיִּקְחוּ־אֶ֛בֶן וַיָּשִׂ֥ימוּ תַחְתָּ֖יו וַיֵּ֣שֶׁב עָלֶ֑יהָ וְאַהֲרֹ֨ן וְח֜וּר תָּֽמְכ֣וּ בְיָדָ֗יו מִזֶּ֤ה אֶחָד֙ וּמִזֶּ֣ה אֶחָ֔ד וַיְהִ֥י יָדָ֛יו אֱמוּנָ֖ה עַד־בֹּ֥א הַשָּֽׁמֶשׁ׃ (יג) וַיַּחֲלֹ֧שׁ יְהוֹשֻׁ֛עַ אֶת־עֲמָלֵ֥ק וְאֶת־עַמּ֖וֹ לְפִי־חָֽרֶב׃ {פ}
(8) Amalek came and fought with Israel at Rephidim. (9) Moses said to Joshua, “Pick some troops for us, and go out and do battle with Amalek. Tomorrow I will station myself on the top of the hill, with the rod of God in my hand.” (10) Joshua did as Moses told him and fought with Amalek, while Moses, Aaron, and Hur went up to the top of the hill. (11) Then, whenever Moses held up his hand, Israel prevailed; but whenever he let down his hand, Amalek prevailed. (12) But Moses’ hands grew heavy; so they took a stone and put it under him and he sat on it, while Aaron and Hur, one on each side, supported his hands; thus his hands remained steady until the sun set. (13) And Joshua overwhelmed the people of Amalek with the sword.
כאשר ירים משה ידו. וְכִי יָדָיו שֶׁל מֹשֶׁה נוֹצְחוֹת הָיוּ הַמִּלְחָמָה וְכוּ' כִּדְאִיתָא בְּרֹ"הַ:
כאשר ירים משה ידו WHEN MOSES LIFTED UP HIS HAND — But could Moses’ hands win the battle etc.? See the whole passage as it is given in the Treatise Rosh Hashanah 29a.
והיה. יש אומרים כי הרמת ידו כאשר יעשה במלחמה מי שבידו הנס. ואלו היה כן מרים אותו אהרן או חור או יעמידוהו במקום גבוה בהר שיראה עומד. והנכון מה שאמרו קדמונינו:
AND IT CAME TO PASS. Some say that Moses held his hand up in a manner similar to one holding up a banner in war. However, if this was the case then Aaron or Hur would have lifted the rod up or they would have placed it on a high place on the mountain so that the people would see it standing. The correct interpretation is the one offered by the ancient sages.
מַתְנִי׳ ״וְהָיָה כַּאֲשֶׁר יָרִים מֹשֶׁה יָדוֹ וְגָבַר יִשְׂרָאֵל וְגוֹ׳״, וְכִי יָדָיו שֶׁל מֹשֶׁה עוֹשׂוֹת מִלְחָמָה אוֹ שׁוֹבְרוֹת מִלְחָמָה? אֶלָּא לוֹמַר לָךְ: כׇּל זְמַן שֶׁהָיוּ יִשְׂרָאֵל מִסְתַּכְּלִין כְּלַפֵּי מַעְלָה וּמְשַׁעְבְּדִין אֶת לִבָּם לַאֲבִיהֶם שֶׁבַּשָּׁמַיִם — הָיוּ מִתְגַּבְּרִים, וְאִם לָאו — הָיוּ נוֹפְלִים.
MISHNA: Incidental to the discussion of the required intent when sounding the shofar, the mishna cites the verse: “And it came to pass, when Moses held up his hand, that Israel prevailed; and when he let down his hand, Amalek prevailed” (Exodus 17:11). It may be asked: Did the hands of Moses make war when he raised them or break war when he lowered them? Rather, the verse comes to tell you that as long as the Jewish people turned their eyes upward and subjected their hearts to their Father in Heaven, they prevailed, but if not, they fell.
From this we can learn that we can achieve everything with trust in 'ה and in ourselves. If the Jewish people hadn't seen Moshe's hands, they would have lost their trust and the war.