Shaykh TusÄ« has narrated from RaÅ¡Ä«q (MarezÄni) that:
The caliph Mu’tadid asked for me and two others, and ordered us to pick two horses with us; one to ride and one as spare. Then we will go lightly and immediately to Samarra and addressed us to the house of His Majesty ImÄm Ḥasan AskarÄ« (PBUH). He also said that there will be a black slave sitting next to the door when you reach there. There,  break into the house and bring me the head of everyone you will find there.
When we reached His Majesty’s house, a black slave was sitting in the corridor of the house, holding a string of underwear and weaving it. We asked, ‘Who is in the house?’, he returned, ‘Its owner!’. He did not take notice of us and was not [even] afraid of us! When we get into the house, we found it a very clean house. On the front side, we saw a curtain, we had never seen better than it. It was as if, it had been just made by a worker. Anyway, There was no one in the house.
When I pulled the curtain aside, it was a big chamber where it seemed a sea is placed inside there. Â And at the end of the chamber, a mat was spread out over the water. On the mat, a man was standing who was the best of people according to dignity. He was praying and did not pay attention to us at all. Ahmad ibn ‘Abdallah stepped into the chamber to enter, [but] he was about to be drowned. He was got so anxious that I stretched out my hand and brought him out. Â Then he fainted!
He woke up after an hour. Then the other man willed to enter and the same thing happened to him. So, I was surprised and I began to apologize. I said, ‘I apologize to God and to you, who are close to God! By God, I did not know who I would be visiting, and I did not know the truth. Now, I repent to God for what I have done.’ [But] he was praying and did not notice my words at all.
We felt great awe in our hearts, then we returned while ‘Mu’tadid’ was waiting for us. He had ordered the guards to take us to him, whenever we got back. Then, we arrived in the middle of the night, went in, and told him the whole story. He asked, ‘Did you meet anyone else before me or talking to anyone?’. We replied, ‘No!’. So he took great oaths that ‘If I hear that you would tell a single word of that story to anyone else, I will behead you all instantly’. So, we could not narrate that story until after his death.