John Gill Commentary Exodus 17:3

"And the people thirsted there for water; and the people murmured against Moses, and said, Wherefore hast thou brought us up out of Egypt, to kill us and our children and our cattle with thirst?" — Exodus 17:3 (ASV)

And the people thirsted there for water
They saw there was no water when they first came thither, and therefore scolded Moses for bringing them to such a place, where they could not subsist; and having stayed some little time here, and all the water they brought with them from Alush being spent, and having none to drink, began to be very thirsty:

and the people murmured against Moses ;
became more impatient and enraged, and threw out their invectives against him with much acrimony and severity:

Why have you brought us up out of Egypt ?
where it would have been much better for us to have continued:

to kill us and our children and our cattle with thirst :

which is intolerable to any, and especially to children and cattle, which require frequent drinking: they could not suppose that Moses had such a murderous view in bringing them out of Egypt, or that this was his intention in it, but that this would be the issue and event of it.