Rashi comments that Moshe changed his name and davened that Hashem should save Yehoshua from the עצת המרגלים.
This is very difficult for a number of reasons:
1. We see clearly from Rashi that Moshe knew that the Meraglim would sin, that is why he davened that Yehoshua would not be caught up in it. If so, why did he send them at all? After all Rashi comments שלח לך that Hashem gave Moshe the choice as to whether to send meraglim or not. If he knew they would sin why didn't he just cancel the mission?
2. Why daven only for Yehoshua? Yehoshua was probably the greatest of the meraglim, why would Moshe worry that he would sin? At the time that they were picked all of the Meraglim were tzadikim, why didn't Moshe daven for all of them?
I did not find any of the meforshim on Rashi that dealt with the first question that if Moshe knew they were going to sin why send them. The Netziv does ask this question and because of this question says that Rashi's pshat is very difficult. In fact, he rejects Rashi's pshat and offers his own pshat.
The meforshim do deal with the second question but I didn't see any convincing answers.
Any thoughts would be appreciated.