Charles Ellicott Commentary Numbers 21:5

"And the people spake against God, and against Moses, Wherefore have ye brought us up out of Egypt to die in the wilderness? for there is no bread, and there is no water; and our soul loatheth this light bread." — Numbers 21:5 (ASV)

This light bread.— The word rendered light denotes something vile or worthless. It was thus that the Israelites regarded the manna which was given to them from heaven; even as the “spiritual meat” which is given to Christ’s Church in His word and ordinances is too commonly regarded among us.