Before us is Mishnah 8 of Maseches Taanis, one of the most famous mishnayos in the tractate, in which one of the best known stories in the words of Chazal is recorded.
The Mishnah opens: "Al kol tzarah shelo tavo al hatzibur, matri'in aleha b'shofaros" - for any trouble that should not come upon the community, the alarm is sounded with shofaros. The phrase "that should not come" is said the way people say "may it never happen." And the Mishnah concludes: "chutz merov geshamim" - except for an excess of rain.
The expression "an excess of rain" needs to be understood precisely: it refers to rain that is a nuisance to people, not to an actual flood, since a flood is certainly a trouble for which the alarm is sounded. But rain that falls more than is needed, that makes walking difficult, fills the roads with mud and requires rain gear, over that one does not pray.
The story of Choni HaMe'agel:
It once happened in a year of drought that the people said to Choni HaMe'agel (we will yet see why he was called by that name): pray that rain should fall. He said to them: go out and bring in the ovens used for roasting the Pesach offering, for those ovens are made of clay, and in the downpour that will come after my prayer they will dissolve.
He prayed, and no rain fell. What did he do? He drew a circle on the ground and stood inside it. He said before the Holy One, blessed is He: Master of the world, Your children have turned their faces to me, that is, they have appealed to me, because I am like a member of Your household and very close to You. "Nishba ani b'Shimcha hagadol she'eini zaz min ha'ugah hazo ad shetracheim al banecha" - I swear by Your great Name that I will not move from this circle until You have mercy on Your children and on Your young ones.
The rain came down in three stages:
Dripping: The rain began merely to drip. He said before the Holy One, blessed is He: this is not what I asked for, but rather rain that will fill all the pits, springs and caves.
Fury and storm: The rain began to fall with great fury and in a great storm. He said: this too is not what I asked for, but rather rain that expresses Hashem's readiness to do good with us, rain of blessing, generosity and giving.
Rain as it should be: From that moment the rain fell properly.
The request to stop the rain:
The rain kept falling until the people of Israel were forced to leave the ordinary part of Jerusalem and go up to the Temple Mount, which was higher ground. They came and said to him: just as you prayed that the rain should fall, so pray that it should go away. He said to them: go out and see whether the Stone of the Claimants has been washed away, a stone that stood in a high place in Jerusalem, upon which a person who had lost an object would stand and announce his loss. This was certainly an expression of exaggeration, for that stone would never be covered; rather, he wished to convey to them that such a thing would never happen, and that he was not going to pray about an excess of rain.
The Gemara fills in what happened at that time: he said to them, I have a tradition that one does not pray over an excess of good. He said to them: bring me a bull of thanksgiving, an ox that we will offer as a korban todah. They brought it before him, he leaned his two hands upon it and said: Master of the world, Your people Israel, whom You took out of Egypt, cannot endure either an excess of good or an excess of calamity. May it be Your will that You hold back the rain and that there be relief in the world. Immediately a wind blew, scattered the clouds, and the sun shone.
The response of Shimon ben Shetach:
After the episode, Shimon ben Shetach, who headed the Sanhedrin, said to him: were you not Choni, I would decree excommunication upon you for the audacity with which you spoke to the Holy One, blessed is He. But what can I do to you, for you plead before the Omnipresent and He does your will, like a son who pleads before his father and his father does his will. Of you the verse in Mishlei says: "Your father and your mother will rejoice, and she who bore you will be glad."
In summary: In this Mishnah we learned that for any trouble that comes upon the community the alarm is sounded with shofaros, except for an excess of rain, for one does not pray over an excess of good. We examined the story of Choni HaMe'agel, who drew a circle and stood inside it until he was answered, the three stages in which the rain fell, his refusal to pray that it stop until he brought a bull of thanksgiving and leaned his hands upon it, and the words of Shimon ben Shetach about that son who pleads before his father and his father does his will.