Commentary for Numbers 21:5

באלהים ובמשה [AND THE PEOPLE SPAKE] AGAINST GOD AND AGAINST MOSES — They placed the servant on a par with his Master (Midrash Tanchuma, Chukat 19).

וידבר העם באלוקים ובמשה, The people spoke out against G'd and against Moses. Although the people were perfectly aware that everything Moses did he did at the command of G'd, this did not prevent them from speaking out against him as they felt he should not have agreed with G'd's route for them but should have pleaded that G'd lead them through a more hospitable country. It would appear that the people's complaints in this instance did not justify G'd decreeing a major punishment as was the case when they had complained after hearing the majority report of the spies in Numbers 14,3. At that time the Israelites had demanded to return to Egypt. This time they "merely" indulged in slander against Moses and G'd. G'd punished them by letting snakes loose against them, seeing snakes symbolise slander ever since the time Eve was tricked by a snake into eating from the tree of knowledge (compare Taanit 8).

הקלקל, extremely lightweight.