What is Tzedah?
Rashi: It is everything needed for the road, and weapons for the war; he told them to prepare them. Do not say that it is food. The manna in their Kelim lasted until Nisan 16, like it says "va'Yishbos ha'Man mi'Macharas" (5:12). 1
Radak: It is food other than bread, for the manna still fell until the day after Pesach. This is also according to Chazal, that it stopped on the day that Moshe died, for the last day's manna lasted until Pesach. 2
Yalkut Shimoni 7: It cannot be food, for they collected manna each morning! Rather, repent, so you will enter the land and eat the land's produce.
Malbim: It is preparing the manna, e.g. grinding it.