In much of the Bible the word Israel means the Chosen People, which means the people who choose to serve God and humanity. This is why it says Israel is a nation of priests. Priests means ministers and ministers means those who serve others.
ORDINATION
It's surely not necessary to be ordained in order to serve humanity, but being ordained is more impressive to some people, so you are welcome to get ordained if you prefer and if you truly intend to serve humanity.
You can get ordained for free if you want to at Universal Life Church. Their creed is simply to Do that which is Right.