Rashi on Numbers 14:29/רש"י על במדבר י״ד:כ״ט

1וכל פקדיכם לכל מספרכם AND ALL OF YOU THAT WERE NUMBERED IN ANY COUNTING OF YOU — i.e. all that are numbered of you in any census (מספר) in which you are numbered, as, for instance, on going to or coming back from war, or when giving the shekels: all who are numbered in all these censuses shall die, and these are, everyone מבן עשרים שנה וגו׳ FROM TWENTY YEARS OLD AND UPWARDS — The age is expressly mentioned to exclude the tribe of Levi because those who were numbered of them were not from twenty years old and upwards (but they were either numbered from one month old — cf. Numbers 3:40, or from thirty years old; Numbers 4:3) (Bava Batra 121b).