The Calligrapher Hafiz Osman And His Works Topkapi Palace – Chapter 2,
When at eighteen years old he received his ‘Icazet’ diploma from Suyolcuzade he could write as beautifully as his teachers and was developing his skill further each day. He was invited to the houses of famous scholars and artists of the day but was too humble to exult at his success. He worked even harder, developing his art step by step. As time passed his fame grew, and the Korans which he wrote were worth their weight in gold. However, Hafiz Osman was not interested in money. Most of the time he was penniless. On the day he was going to go and visit a friend who lived in Uskudar. He got in the boat and crossed to the other side. When it came to paying the boatman he put his hand in his pocket but there was no money, and there was the boatman waiting with his hand held out. “Wait”, he said to the boatman “and I’ll write a Besmele (a prayer) for you!” He took a pen and paper out of his pocket and squatted on the ground. He drew a beautiful Besmele and handed it to the boatman: “I apologize my friend. I forgot to bring any money with me. Let this Besmele be a gift to you.” As Osman walked off the boatman looked in astonishment at the paper in his hand, thinking to himself: “Is this man crazy or something? What use to me is this piece of paper…” With the paper in his hand, he entered the nearby coffee house, where someone noticed the paper in his hand. “That’s the writing of Hafiz Osman. Where did you get it from? Sell it to me…” Someone else also became interested, and one by one the number of people wanting to buy the paper increased. In the auction, the price went up to five pieces of gold, and the boatman who did not understand in the least what was going on was left staring in astonishment at the five pieces of gold in his hand. Then he saw Osman once again on the shore searching for a boat. He ran over to him and kissed his robes. He brought his boat over and took Osman over to the other shore.
You can find more details about The Calligrapher Hafiz Osman And His Works in Chapter 3.