"From thirty years old and upward even until fifty years old, all that enter into the host, to do the work in the tabernacle of the congregation.
From thirty years old and upward even unto fifty years old, every one that came to do the service of the ministry, and the service of the burden in the tabernacle of the congregation."
Some variation of this verse is mentioned seven times in this chapter. There must be something about being thirty. I read the footnote.
"And Jesus himself began to be about thirty years of age, being (as was supposed) the son of Joseph, which was the son of Heli," (Luke 2:23)
It appears to be a type and shadow of when the Savior would also begin his ministry. I thought about when I was thirty. I was recovering from my near-death experience. It was a birthday I thought I would never see. I think I needed to be thirty to go through that. Wise enough to be an adult with some experience, but young enough to still be moldable. Of course, I wasn't called to a ministry, but I can see the wisdom of beginning service to the Lord at that age.
It makes me think about a discussion I had during family scripture reading with my son in his thirties. We were talking about how some people say they feel inside like they are still a teenager or young adult. We all agreed we don't feel that way at all. At the time I couldn't figure out what age I felt like. I just felt like me. Thinking on it now I think I'm stuck at thirty on the inside, but getting smarter as the years go by.