Guru Nanak Dev Ji And The Dried Up River
Guru Nanak Dev Ji had a dialogue with the Sidhs near where Gurudwara Nanak Mtah Sahib is. When Guru Ji went there, the Sidhs, using their supernatural powers dried up all the water.
Guru Ji directed his disciple to place the end of a stick at the point where the river-flow commenced and to start walking downstream and trailing the stick behind him. Guru Ji told his disciple that the river water will follow the stick automatically. However, Guru Ji admonished him from turning around and looking behind.
Bhai Mardana did as he was told, but after progressing halfway an element of doubt beset his mind - is the river water really following his stick? He looked back, and to his utter surprise Bhai Mardana saw that the river water was indeed flowing down behind the stick but had ceased flowing on his looking back. Bhai Mardana became depressed and ashamed that he had not obeyed his Guru Ji's advice.
When he returned to Guru Nanak Dev Ji, the latter asked him what happened to the river water that he was supposed to bring back with him? With profound apologies, he told his Guru Ji that his faith had faltered halfway through the journey and he had looked back; the river water then receded. Guru Ji told Bhai Mardana that his motive was to show him the power of faith, and told him that the power was in his (Guru Ji's) bachan or words and not in the stick which Bhai Mardana had been dragging behind him.
From: Divine Mystic Reflections on Gurmat Book - Talks & Dialogues by Saint Scholar Naranjan Singh Ji