דברים א:כז פירוש: רש״י, ספורנו, רשב״ם וSiftei Chakhamim

ותרגנו — This is an expression denoting slander. Similar is, (Proverbs 18:8) “The words of a נרגן” i.e. of a man who brings a false report (Sifrei Devarim 24:1).

בשנאת ה' אותנו, because we had worshipped idols while we were in Egypt.

ותרגנו, the word is derived from the same root as Proverbs 18,8 דברי נרגן כמתלהמים, “the words of a quarrelsome man are like afflictions.”