Yea, they spake against God; they said, Can God furnish a table in the wilderness? Behold, he smote the rock, that the waters gushed out, and the streams overflowed; can he give bread also? can he provide flesh for his people? - Psalm 78:19-20 I actually think their complaining was beyond food, but the uncertainty of the future. They did trust God enough for the abundant life they want and have been promise them. The thought of moving from one place to another, with obstacles on their way, eating manna all their life becloud their reasoning, after they have failed the initial test, when 10 out the 12 persons sent to spy Canaan land brought back an evil report. Remember, there was no case that it has happened this way to any group of individuals before, except stories and promises. Also, the devil was working behind the scene, instigating them to doubt and rebel against God. So you may want to sympathize with them. Because we may have done more so. In life, there maybe doubt as ...
"But if our gospel be hid, it is hid to them that are lost:" 2 Corinthians 4:3