Ibrahim bin Adham (rahmatullah alaih) relates:

Once I passed by a shepherd and asked him, "Do you have any water or milk?"
The shepherd replied, "Yes, which would you like?"
I said, "water."
The shepherd turned and walked up a hill.
I followed.
We reached a plateau, where several boulders had settled.
The shepherd gently struck one of the boulders with his staff and moved back.
The boulder cracked and water gushed forth.
I drank to my fill and also took the opportunity to fill my cistern.
This amazed me.
The shepherd, noticing my amazement, said, "Do not be astonished. When a servant becomes obedient to his Lord everything becomes subservient to him."

Taken from Stories of the Pious by Shaikh Ahmad Ali