Imam Baqir (a.s.) related:
Once, a group of Muslims had set off on a journey, but in the course of their travel, they lost their way. Their supplies were soon exhausted and they were overcome by intense thirst.
(With no water in sight and imagining their end to be near) they put on their shrouds and sat down, resting themselves against the trees.
Suddenly, an old man in white apparels approached them and said:
“Arise, for you have nothing to fear. Here is some water for you.”
They scrambled for the water and drank to their fill after which, turning to the old man, they said, “May God have mercy upon you! Who are you?”
“I belong to the Jinn community, who had pledged allegiance to the Holy Prophet (s.a.w.). I had heard him say: ‘A Mu’min is the brother of another Mu’min. He is his eyes and his guide (too).’ I could not allow you to die of thirst, while I was here.”( Al-Kafi, vol. 2, ‘The Chapter of Brotherhood of the Mu’mineen’, tr. 10.)