143 Taanit 1/2-5

(2) We do not ask for rain, unless it is near [or during] the rains. Rabbi Yehudah says, "He who passes in front of the ark [the chazzan] on the last day of the festival [Shmini Atzeret], the last one [the chazzan who does the Musaf service] mentions [that G-d brings rain], but the first one [the one who does the Shacharit service] does not. On the first day of Passover, the first [chazzan] still mentions it, but the last one does not." Until when is the rain to be prayed for? Rabbi Yehudah says till after the Passover; Rabbi Meir says till the month of Nissan has passed, because it is said [Joel 2:23], "And he will cause to come down for you the rain, the early rain and the late rains in the first month."

(3) On the third of Mar-Cheshvan prayers for the rain are to be said, but according to Rabbon Gamaliel, on the seventh of the same month, namely, fifteen days after the feast of tabernacles, in order that the last Israelites might have reached the river Euphrates.

(4) If the seventeenth of Mar-Cheshvan has come without the rain having yet descended, private individuals commence to keep three fast-days. On the night beforehand, they are allowed to eat and drink, and it is allowed [on the fast day itself] to work, to bathe, to anoint the body, to wear [leather] shoes, and to perform the marriage duty.

(5) If the new moon of Kislev has arrived without the rain having yet descended, the Beth Din (law court) shall order three public fast days. On the night beforehand, we may eat and drink, and it is allowed [on the fast day itself] to work to bathe, to anoint the body, to wear [leather] shoes, and to perform the marriage duty.