וְאָמַ֤ר אֲלֵהֶם֙ שְׁמַ֣ע יִשְׂרָאֵ֔ל אַתֶּ֨ם קְרֵבִ֥ים הַיּ֛וֹם לַמִּלְחָמָ֖ה עַל־אֹיְבֵיכֶ֑ם אַל־יֵרַ֣ךְ לְבַבְכֶ֗ם אַל־תִּֽירְא֧וּ וְאַֽל־תַּחְפְּז֛וּ וְאַל־תַּֽעַרְצ֖וּ מִפְּנֵיהֶֽם׃
and shall say unto them: ‘Hear, O Israel, ye draw nigh this day unto battle against your enemies; let not your heart faint; fear not, nor be alarmed, neither be ye affrighted at them;
Rashi on Deuteronomy
שמע ישראל [AND HE SHALL SAY UNTO THEM] HEAR O ISRAEL — Even though you have no other merit than the fulfilment of the command of “Reading the Shema” you would deserve that He should help you (Sotah 42a).
Rabbeinu Bahya
שמע ישראל, אתם קרבים היום למלחמה, “Hear o Israel! Today you are approaching battle.” The priest implies that the intoning of the Keriyat Shema will be a major factor in securing victory as this paragraph deals with the Oneness, Uniqueness, and Unity of Hashem. אל תיראו, “do not be afraid,” in your heart. ואל תחפזו, “and do not panic.” This is an expression describing an accelerated heartbeat due to fear. The word appears as meaning speed in Samuel I 23,26 נחפזת ללכת, “you were in too much of hurry to go.” ואל תערצו, “and do not become broken,” i.e. physically.