Why did Moshe instruct the Spies to ascend via the Negev?
Rashi: Because it was the most inferior part of Eretz Yisrael, and merchants tend to first display the poor-quality goods before taking out the best.
Ramban, Seforno (in Pasuk 2) and Targum Yonasan: Because they were currently encamped south of Eretz Yisrael (and it made no sense to make a detour and to begin from anywhere else- Seforno). 1
Ramban: And it was important to prepare themselves according to the strength of the enemy when they began the conquest of Cana'an.