Exodus 17:7

And he called the name of the place Massah, and Meribah
The former signifies "temptation", and the latter "contention": the reason of which names being given by Moses, or whoever was the name of the place, follows: "because of the chiding of the children of Israel"; that was the reason why it was called by the last name, Meribah, because here, the Israelites chid and contended with Moses, and used him opprobriously:

and because they tempted the Lord;
therefore it had the former name of Massah:

saying, is the Lord among us or not?
as if they should say, if we perish through thirst, the Lord is not among us, nor takes any care of us; nor was it he that brought us out of Egypt, but Moses; nor is he in the pillar of cloud and fire, as is said; but if he works a miracle, and gives us water, for us, our children, and cattle, then it will appear he is among us; and thus they tempted the Lord, though without this they had full proof, by many instances, that he was among them, and even in a very extraordinary manner.