They Won't Let Me Go!

In the time of the Prophet, a certain unbeliever had a Muslim slave who was a man of true substance. One morning the unbeliever ordered his slave, “Fetch basins. I am going to the baths.”
On the way they passed by the Prophet praying in the mosque with his companions. The slave said, “Master, for God’s good sake take this bowl for a moment, so that I can make a few genuflections, then I will attend to you.”
Entering the mosque, he prayed. The Prophet came out with his companions. The slave remained alone in the mosque. His master waited for him till mid-morning, then he shouted, “Come out, slave!”
The slave answered, “They won’t let me go, as the work has gone beyond bounds.”
The master put his head inside the mosque to see who it was that would not let the slave go. Except for a shoe and a shadow he saw no one. Nobody stirred. He said, “Well, who is it that won’t let you come out?”
 The slave replied, “The same One who will not allow you to come in, the very same One whom you cannot see.”
Fihi Ma Fihi Discourse 26