וְשָׁמְע֖וּ לְקֹלֶ֑ךָ וּבָאתָ֡ אַתָּה֩ וְזִקְנֵ֨י יִשְׂרָאֵ֜ל אֶל־מֶ֣לֶךְ מִצְרַ֗יִם וַאֲמַרְתֶּ֤ם אֵלָיו֙ יְהוָ֞ה אֱלֹהֵ֤י הָֽעִבְרִיִּים֙ נִקְרָ֣ה עָלֵ֔ינוּ וְעַתָּ֗ה נֵֽלֲכָה־נָּ֞א דֶּ֣רֶךְ שְׁלֹ֤שֶׁת יָמִים֙ בַּמִּדְבָּ֔ר וְנִזְבְּחָ֖ה לַֽיהוָ֥ה אֱלֹהֵֽינוּ׃
און זײ װעלן צוהערן צו דײַן קָול, און װעסט קומען, דו און די עלטסטע פֿון ישׂראל, צו דעם מלך פֿון מִצרַיִם, און איר װעט זאָגן צו אים: ה׳, דער גאָט פֿון די עִבֿרים, האָט זיך געטראָפן פֿאַר אונדז. און אַצונד, לאָמיר גײן, איך בעט דיך, דרײַ טעג װעגס אין דער מדבר, כּדי מיר זאָלן שלאַכטן צו ה׳ אונדזער גאָט.
Rashi
ושמעו לקלך AND THEY SHALL HEARKEN TO THY VOICE — as soon as you will mention to them this expression (the double use of the verb פקד as in v. 16) they will hearken to your voice, for they have long had this sign as a tradition from Jacob and Joseph that by mention of this phrase their deliverance will be brought about. Jacob said to them “And God will surely visit you”, and Joseph said to them (Genesis 50:25) “God will surely visit you”.
Chizkuni
ושמעו לקלן, “they will listen to you (and believe you).” Rashi explains that the reason that the people will immediately believe Moses was that they had a tradition going back to Yaakov according to which their eventual saviour would introduce himself by referring to G-d as having used the words: פקוד פקדתי אתכם, “I have surely remembered you.” Actually, Rashi is not correct, as that tradition only went back to Joseph having used these word in Genesis 50,25.
Da'at Zekenim
ושמעו לקולך, “they will listen (obey) to your voice.” According to Rashi, the Jews had already been given the code word with which their eventual redeemer would identify himself when both Yaakov and Joseph used the root word פקד in connection with the time of their redemption from slavery in Egypt. I explained this on Genesis 50,24 and 25. Some people raise the question that actually we have no record of Yaakov having said: פקוד יפקוד. According to my explanation on that verse the question has been answered satisfactorily.