וַֽתַּעֲנ֣וּ ׀ וַתֹּאמְר֣וּ אֵלַ֗י חָטָאנוּ֮ לַֽיהוָה֒ אֲנַ֤חְנוּ נַעֲלֶה֙ וְנִלְחַ֔מְנוּ כְּכֹ֥ל אֲשֶׁר־צִוָּ֖נוּ יְהוָ֣ה אֱלֹהֵ֑ינוּ וַֽתַּחְגְּר֗וּ אִ֚ישׁ אֶת־כְּלֵ֣י מִלְחַמְתּ֔וֹ וַתָּהִ֖ינוּ לַעֲלֹ֥ת הָהָֽרָה׃
Entonces respondisteis y me dijisteis: Pecado hemos contra SEÑOR; nosotros subiremos y pelearemos, conforme á todo lo que SEÑOR nuestro Dios nos ha mandado. Y os armasteis cada uno de sus armas de guerra, y os apercibisteis para subir al monte.
Rashi on Deuteronomy
ותהינו — This is an expression derived from the word הננו in (Numbers 14:40) "Here we are (הננו) and we will go up to the place”. This is the expression which you uttered — the expression הן, "yes”. The word, therefore, means as much as: you expressed your readiness to go up into the mountain.
Ramban on Deuteronomy
ANACHNU’ (WE) ‘NA’ALEH’ (WE WILL GO UP) AND FIGHT. The purport of the word ‘anachnu’ (we) [when it is already included in the word na’aleh which means “we will go up”] is that “we ourselves” will go up and we will fight, and we will not leave the matter to our children after us, as you [Moses] have said.
Rashbam on Deuteronomy
ותהינו, meaning הננו, “we are ready, prepared;” the people at that point were willing to ascend. (Numbers 14,40)