Numbers — Chapter 4

The Levites serve from age thirty to fifty; Lapide notes that among the Hebrews no one could teach before age thirty — hence both Christ and John the Baptist began their public preaching at thirty, \"the age of mature judgment and rightful authority.\"

The office of the Kohathites is to carry the most sacred vessels — the Ark, the altar, the candlestick — on their shoulders; no cart is allowed for these, signifying that sacred things must be borne by those specially consecrated.