Rashi on Deuteronomy 1:41/רש"י על דברים א׳:מ״א

1ותהינו — 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.