Numbers 20:3 Commentary: Rashi, Sforno, Or HaChaim & Rabbeinu Bahya

ולו גוענו — means, WOULD THAT WE HAD DIED.

וירב העם עם משה, the subject of the quarrel was why Moses had brought the people to such a desert as the one they found themselves in at the time. However, there was also a complaint against G’d Himself, as the Torah testifies in verse 13 where the Torah writes: אשר רבו בני ישראל את ה', “in that the Children of Israel quarreled with G’d.” This referred to the words (verse 5) “why did you take us out of Egypt?”

וירב העם עם משה, The people quarrelled with Moses. The people now complained that they would have preferred for Moses to have let them die from the plague than to face death by thirst.