41 بابُ اِستِسقاءِ الْمَأمُون بِالرِّضا عَلَيْهِ السَّلامُ...
Some of the people close to Al-Ma’mun and those biased against Ar-Ridha’ (a.s.) said, “See that God has withheld rain from us since Ali ibn Musa (a.s.) came to us and was designated as the successor to the throne.” The word got around to Al-Ma’mun and it was unpleasant for him. He told Ar-Ridha’ (a.s.), “It has not rained. Please pray to God the Honorable the Exalted to send down rain for the people.” Ar-Ridha’ (a.s.) said, “Fine.” Al-Ma’mun asked, “When will you do that?” It was Friday.
Ar-Ridha’ (a.s.) replied, “On Monday. I saw my grandfather - God’s Prophet (S) - in my dreams along with the Commander of the Faithful (Imam Ali (a.s.)). The Prophet (S) said, O my son! Wait until Monday. Then go to the desert and pray for rain. God the Highest will send down rain. Inform the people regarding your rank among them which God shows you but the people are unaware of.
Thus they will be able to recognize you and become more knowledgeable about you; and recognize your rank and credibility near your Lord - the Honorable the Exalted.” On Monday, Ar-Ridha’ (a.s.) went to the desert. The people came out to watch. He climbed up the pulpit, praised God and glorified Him. Then he (a.s.) said, “O God! O Lord!
Thee glorified the rightfulness of us - the Members of the Holy Household, so that the people ask us for help according to Thy decree hoping to receive Thy Nobility and Thy Mercy. They expect Thy Kindness and Blessings. Then please send them rain - a bountiful rain, with extensive coverage, immediately and unharmful.
After they leave, please let it start to rain where they are watching from, and from the time they get back home.” The narrator added, “By the One who rightfully appointed Muhammad (a.s.) to the post of Prophethood!