אבן עזרא — מה תריבון עמדי מה תנסון את ה' / מסה ומריבה

Q — At Refidim the people complain about water and Moshe responds "מה תריבון עמדי מה תנסון את ה'" — and the place is then named "מסה ומריבה." But if the people had no water, what testing of God is going on? They're thirsty!

A — Ibn Ezra picks up a textual signal: the verse says "וירב העם" (the people), not "כל העם" (all the people, as in the manna episode). Two distinct groups: one truly out of water — who fought Moshe (מריבה); a second group that still had water saved from the previous stop at Alush — who deliberately TESTED God to see if He would provide (מסה). Moshe addresses each group separately: "מה תריבון עמדי" (to the thirsty — fighting won't help, we'll all call out to God), "מה תנסון את ה'" (to the testers). The double name follows: מסה for the testers, מריבה for the strivers. Bonus: the chiastic "מסה ומריבה / על ריב בני ישראל / ועל נסותם את ה'" — Ibn Ezra notes "משפט לשון הקודש" that Tanach typically explains the LATER-mentioned item first. And the warning in Devarim ("לא תנסו את ה' אלקיכם כאשר נסיתם במסה") names only מסה — the testing was the worse sin.