RC Sproul shares the story of Peter Beskendorf, a barber who was in his shop one day and noticed a man come in and take his seat. As the barber took out his straight razor and as he was stropping it to hone it to a razor’s edge, he noticed that the man who had entered his shop was a fugitive. He was wanted. There was a price on his head. And the man was one of the most hated men in the whole continent.

And when he took his place to have his hair cut and his beard shaved, the barber took that razor, pressed it against the edge of the man’s neck, and knew that if he just put a little more pressure on the blade, he could become famous and rich for collecting the reward.

But he made no move to exert such pressure on the patron’s neck, because despite the hatred the customer bore, the barber loved him and considered one of his greatest heroes, and considered himself blessed that he would even have the earthly privilege of shaving the face of Martin Luther. Luther came to Master Peter’s shop on a regular basis for the haircut and the shave.

And when Master Peter had Martin Luther as a captive audience, he would spend the time asking the great Reformer theological questions. One day he raised the question of prayer and said to Martin Luther, “Dr. Luther, can you teach me how to pray?”

Luther said, “I’d be glad to Master Peter”, and he went back to his room at Wittenberg and he picked up a pen, and specifically for his barber he wrote a short little essay entitled "A Simple Way to Pray". You can read about it here:

http://www.thegospelcoalition.org/publications/34-3/deliver-us-from-the-...

Incidentally, have you ever wondered why we have to pray if God already knows everything? Well here's a five minute video by DA Carson that provides an answer:

http://thegospelcoalition.org/resources/video/What-is-biblical-prayer-Wh...