Sforno on Exodus 17:2/ספורנו על שמות י״ז:ב׳

1מה תריבון עמדי?; do you not know that I do not act arbitrarily but only carry out G’d’s orders?

2'מה תנסון את ה?; if you really quarrel with me, this is equivalent to your quarrelling and testing the One whose agent I am. You are only endangering your own lives if you quarrel with G’d! If He becomes angry He will consider that He has to destroy you, seeing that He had demonstrated His power to you in deeds. We find Moses repeating this thought in Psalms 95,9 אשר נסוני אבותיכם בחנוני גן ראו פעלי, “when your fathers put Me to the test, tried Me, though they had seen My deeds.” [when someone who had never had a manifestation of G’d’s power “tests” Him, this is far less serious than when the Jewish people who had ample proof of G’d’s power would do the same. Ed]