Once, people suffered from a terrible drought. Al-Mu’tamid, the Abbasid caliph, ordered people to go out in the open air for three days in order to offer the prayer for rain. They did, but no rain fell down.
Christians as well went out with whom there was a monk who whenever stretched his hand towards the sky, it rained. He did that many times and some ignorant (Muslims) doubted their religion and some others apostatized. This was hard for al-Mu’tamid. He went to Imam Abu Muhammad (a.s.) who was in prison then and said to him, ‘Attain to the nation of your grandfather before they will perish!’
Imam Hasan Al-Askari(a.s.) said to him, ‘Let people go out tomorrow and I shall remove their doubts Insha’Allah.’ Al-Mu’tamid set the Imam(a.s) free from prison, but the Imam asked him to set free all his companions from prison too, and al-Mu’tamid agreed to his request.
On the following day, people went out to offer the prayer for rain. The monk raised his hand towards the sky and it clouded and rained. Imam Hasan Al-Askari (a.s.) asked his men to catch the monk’s hand and take what there was in it. There was a bone of a human being. The Imam(a.s.) took the bone from the monk and asked him to pray for rain again. The monk raised his hands towards the sky, but clouds disappeared and the sun shone. People were astonished. Al-Mu’tamid asked Imam Abu Muhammad (a.s.) what that thing was and the imam said, ‘This is a bone of one of the prophets that this monk has got in some way or another from some grave. Whenever a prophet’s bone is exposed under the sky, it will rain…’ Al-Mu’tamid checked that and it was as the Imam(a.s) said. Then suspicions and doubts were refuted.
Jawharat al-Kalam, p.154, Akhbar ad-Duwal, p.117.