The Imām’ Reza (as) Supplication in Asking for Water

Rain was withheld from the people, so some of those who harbored malice against the Imām, peace be on him, ascribed that to his assuming the position of heir apparent. They began announcing and spreading that among the popular circles in order to defame the personality of the Imām, peace be on him. Al-Ma’mūn heard of that and became displeased with it. Then he told the Imām about that, asked him to supplicate Allah for sending down rain to the people. The Imām answered him, saying: “Surely, I will do that on Monday.”
“Why?” asked al-Ma’mūn.
He, peace be on him, replied: “Surely, Allah’s Messenger, may Allah bless him and his family, came to me yesterday nigh, and there was along with him the Commander of the faithful, ‘Ali, peace be on him, and he said to me: ‘My son, wait until Monday (comes). Go to the desert and ask for water, for surely Allah shall water them (with rain), and tell them of what will Allah make you see of what they do not know of their state, that they may be increased in knowledge of your excellence and position with your Lord, the Great and Almighty.”
So al-Ma’mūn and the rest of his personal entourage waited until Monday came. Meanwhile he ordered all the popular classes to go to the desert on Monday. When this day came, the people went in a hurry to the desert. The Imām, who was in the appearance of the prophets, went to the desert. When he arrived in the desert, a pulpit had been installed for him. The people surrounded him and said at the top of their voices: “There is no god but Allah! Allah is great!”
The Imām ascended the pulpit, praised and lauded Allah, and then he said: “O Allah! O Lord! It is You who have magnified our right, the Ahl al-Bayt! So they have sought access through us (to You) as You have commanded, hoped for Your bounty and mercy, expected Your kindness and favor. So give them water with a watering which is useful, general, neither slow nor harmful! And let their rain start after their leaving this view of them to their houses and their abodes!”
The Imām added, saying: “So by Him who sent Mohammed with the Truth as prophet, the wind wove clouds in the air, and it thundered and lightened.”
When the people heard of the Imām’s statement, they intended to go to their houses, lest the rain should befall them. So he, peace be on him, said: “That cloud which has towered over you is not for you; rather it is for another city.” And he mentioned to them the name of the city.
Then ten successive clouds towered over the people, and the Imām told them that each cloud would rain in a certain city, and he mentioned the names of the cities. As a result the eleventh cloud towered over them, so he, peace be on him, said: “O People, that is the cloud which Allah, the Great and Almighty, has sent for you, so thank Allah for His favor toward you; go to your abodes and houses, for it has been sent for you. It has been prevented from raining on your heads until your enter your abodes. Then some good suitable for the munificence of Allah, the Great and Almighty, will come to you.”
Then he descended the pulpit, and the people went in a hurry to their houses. When they arrived at their houses, it began raining heavily. So the valleys, the basins, the streams, and the deserts were filled with water.
The people believed in the miracles of the members of the House (ahl al-Bayt), peace be on them, and their remarkable rank with Allah, the Most High, and said: “We congratulate the children of Allah’s Apostle, may Allah bless him and his family, on the miracles of Allah, the Great and Almighty, toward them.”


Reference :The life of Imām'Ali Bin Mūsā al-Ridā