There is an interesting story of a poor boy who was a student in school. During an annual Father’s Day ceremony, the teacher requested the students to give some kind of a contribution. Formerly teachers would not earn a salary but would receive whatever the students would bring from their parents’ homes or by begging. Generally the brahmanas were teachers, and they could not charge anything. Thus some students brought the teacher rice, and some students brought other crops. One student was so poor that he could think of nothing to bring; therefore he told his teacher that he would speak to his mother first. After school, the student told his mother, “My dear mother, all my class contribute?” The mother replied, “My dear son, we are so poor that we cannot give anything. However, Krishna is the friend of the poor. If he gives you something, you can promise it to your teacher.” “Oh, where is Krishna?” the little boy asked. “Well, I understand that he is in the forest,” the mother said. Therefore the little boy went to the forest and called for Krishna. He then began to cry, and finally Krishna came. When a devotee is very eager to see Krishna, Krishna is so kind that He comes. “So, what are you asking?” Krishna asked the little boy. “You are the friend of the poor,” the little boy said. “I am very poor, and what can I promise my teacher?” Krishna then told him, “You can tell him that you will supply him some yogurt, some dahi.” The little boy was very satisfied with this, and the next day he went to his teacher and said, “I will supply you as much yogurt as you need.” The teacher felt that this was very nice, and he was pleased with the boy. On the day of the ceremony, the boy again went to the forest and called for Krishna. Krishna appeared and gave him a quart of yogurt. The little boy took this yogurt to his teacher and said, “This is my contribution, sir.” The teacher looked at the quart and said, “What is this? Hundreds of people will be coming, and you have only given this much yogurt?” The teacher became so angry that he spilled the yogurt out of the container. When he bent down to pick it up, he saw that the container was again full. He dropped it again, and it was again full. He could then understand that it was spiritual. This is the nature of Krishna. One can take everything, and yet the same will remain. In the material world, one minus one equals zero, but in the spiritual world, one minus one equals one. That is called advaya jnana. There is no duality in the spiritual world. One plus one equals one and one minus one equals one. If we love Krishna, that love will not be destroyed as love will in the material world.
Ref >> Srila Prabhupada Vani.