Numbers — Chapter 8

The seven lamps of the golden candlestick are set so they illuminate the table of showbread; the seven lamps signify the sevenfold gifts of the Holy Spirit illumining the bread of God's word.

Levites serve from age 25 to 50; after 50 they assist their brethren but no longer bear the heavy burdens; a principle of graduated service and honourable retirement for those grown old in sacred ministry.