Rashi on Numbers 17:25/רש"י על במדבר י״ז:כ״ה

1למשמרת לאות TO BE KEPT AS A SIGN — i.e. as a reminder that I have chosen Aaron to be the priest and that they should therefore not murmur any more against the priesthood.

2ותכל תלונתם is the same as וּתְכַלֶּה תלונתם, AND THOU SHALT MAKE AN END OF THEIR MURMURING. This form (תלנֹתם) is a nomen actionis (שם מפעל), singular number, feminine gender, the same as is תלונָתם; in O. F. murmures. But there is a difference in sense between תלנֹתם and תלונָתם. The word תלונָתם denotes a single act of murmuring; תלנתם is a noun with singular meaning although there may be many acts of murmuring.