Interestingly, servant leadership is probably an idea that is most commonly associated with stories of Jesus in the New Testament. When he washes his disciples feet (found in the Gospel of John, chapter 13) he humbles himself in order to be an example. The NIV version puts it this way:
[Jesus said] Do you understand what I have done for you?...Now that I, your Lord and Teacher, have washed your feet, you also should wash one another's feet. I have set you and example that you should do as I have done for you. (vs 12-15)
This is the illustration of the principle Jesus introduces in the Gospel of Matthew, chapter 20, verse 16 "The first shall be last and the last shall be first."
The general idea here was revolutionary in Biblical times (and still is today) because when most people think of leadership, they think of being in charge, working their way to the top, and eventually having servants. The principle Jesus proposes is exactly opposite of what our human tendency is. The natural human inclination is to view positions of leadership as commanding from the top, not participating in the grunt-work.
In life, however, this principle can be proved through practice. Another word for "servant leadership" could be "participatory leadership." Think about the difference between teachers who only teach by giving lectures from a distance and teachers who are at students' desks, helping them think and work out answers with them. Think about getting 2-year-olds to clean up messes. It goes far better when the adult in charge is on the floor demonstrating and helping.
Servant leaders earn respect by putting the needs of others first. They show that they are making decisions for the good of the group, rather than just themselves. Even prime-time television has emphasized the idea with the new show on CBS: "Undercover Boss." As corporation heads take on the challenges of those doing the dirty work, they are able to see and appreciate how their employees feel and what they need.
The concept of servant leader is a very old one although the term was coined by Robert Greenleaf in in his 1970 essay, The Servant as Leader. This term is intended to reflect the fact that the function of a good leader, is to serve and promote the interest of his followers. For example, the Valmiki Ramayana, the Sanskrit epic written several thousands of years back, contains the concept that it is the duty of a king (leader) to promote the welfare of his subjects. This kind of view of the purpose and role of leadership has been promoted by many great people. The answer posted explains how Jesus Christ also supported this view. More recently Mahatma Gandhi, Drawing on the concepts of Valmiki Ramayan, proposed the concept of "Ram Rajya" that embodies the concept of a King or Government as a servant of the people.
The modern servant leadership approach emphasizes collaboration, trust, empathy, and the ethical use of power. The leader is, at heart, a servant first, making the conscious decision to lead in order to better serve others, not to increase their own power. The objective is to enhance the growth of individuals in the organization and increase teamwork and personal involvement. Such a leader needs the to possess qualities like listening, empathy, healing, awareness, persuasion, conceptualization, foresight, stewardship, growth and building community. Acquiring these qualities tend to give the leader authority granted by the people. The leader draws his power from this authority rather than coercive power derived from any external source.