Leadership lessons from Jesus Christ; wisdom from The Gospel of Mark.
Time: Between 1 AD and 30 AD
He sat down and called the around him and said, “Anyone wanting to be the greatest must be the least — the servant of all.” — Mark 9:35
Leaders are servants. This is the source of the politicians calling themselves “public servants”. A leader of any unit of any organization is serving that unit — by providing leadership. Others may provide catering services, maid service, even messenger service; leaders are just like those other service providers. They provide leadership service.
Wikipedia article on the historical Jesus.