the poor dervish was illiterate and wished to learn to read.
He went to a teacher and asked to learn arabic. The teacher agreed to teach for free because of his sincerity, and began to show him the alphabet. He drew a straight vertical line ont he wall and said 'This is the letter alif'. After the first letter the dervish thanked him so much and left before the teacher could tell him about the rest of the letters.
The teacher was astonished and thought thought he would never finish at this rate. The dervish didn;t come back the next day, day after or week after. After a month the dervish showed up again, with a light shining from his eyes and said he was ready for the next lesson. The teacher told him that before going to the next letter he would like to see the dervish show what he had learned.
The dervish wrote an alif on the wall, and the wall crumbled.