מִבֶּן֩ שְׁלֹשִׁ֨ים שָׁנָ֜ה וָמַ֗עְלָה וְעַ֛ד בֶּן־חֲמִשִּׁ֥ים שָׁנָ֖ה תִּפְקְדֵ֑ם כָּל־הַבָּא֙ לַצָּבָ֔א לַעֲבֹ֕ד אֶת־עֲבֹדַ֖ת אֹ֥הֶל מוֹעֵֽד׃
from thirty years old and upward even unto fifty years old shalt thou number them, every one that entereth upon the service, to do the work of the tent of meeting.
Read halakhic rulings (Jewish law) on Numbers 4:30: and classical halakhic sources.