כַּאֲשֶׁר֩ מְרִיתֶ֨ם פִּ֜י בְּמִדְבַּר־צִ֗ן בִּמְרִיבַת֙ הָֽעֵדָ֔ה לְהַקְדִּישֵׁ֥נִי בַמַּ֖יִם לְעֵינֵיהֶ֑ם הֵ֛ם מֵֽי־מְרִיבַ֥ת קָדֵ֖שׁ מִדְבַּר־צִֽן׃ (פ)
Rashi on Numbers
המה מי מריבת קדש THEY, THE WATERS OF MERIBA IN KADESH — they alone were the cause of their death: there was no other sin in them. — Another explanation is: it was they (the waters) which were the cause of their rebellion at Marah (Exodus 16:23-24), it was they which made them rebel at the Red Sea (Exodus 14:11—12) and yet it was they which made them rebel here in the wilderness of Zin.
Rabbeinu Bahya
הם מי מריבת קדש, “they are the waters of strife at Kadesh.” This verse demonstrates that neither Moses nor Aaron had been guilty of any other sin. the word הם, “they,” means “these only and none other.”
Siftei Chakhamim
They had no other sins. That is to say, that they had only the sin of the waters of dispute, but no other sin. Accordingly, this refers to Moshe and Aharon.