Why does the Parsha wrap up with the laws of Tzitzit? And why therefore are women exempt therefrom? Techincally, women are exempt from all time-related mitzvot -- and Tzitzit are only obligatory at night. But...we propose that the parsha ends with Tzitzit since it is the answer to the spies' fears, since wearing Tzitzit will remind you of your mission and you won't be "consumed by the land." Yet the women were never frightened by the words of the spies in the first place and therefore merited to enter the Land. Only the men were told they would have to die in the desert. So...it follows that women are exempt from Tzitzit. See also Kli Yakar on the first verse of the parsha regarding what would have happened in the spies were women instead of men.