The spies were sent to find out, among other things, whether “… there is a tree or not” (Bamidbar 13:20). Rashi explains: “Do they have a proper person, who can shield them with his merit?”
About Bein Hashmashot, the impact on important mitzvot, how will it affect the time of the bris? Dovening Minha, Shabbat, Rosh Hashana, the Gra and Rabbeinu Tam.