Who knows nine?
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Nine are the total number of Cities of Refuge to be designated in the Land of Israel, when its boundaries are broadened (Deut. 19:9).
Incidentally, Maimonides (Laws of Kings 11:2) uses this verse as one of the proofs that the Torah speaks of a future era of Moshiach (may he come soon!), since the broadened boundaries of which this verse speaks have never yet come to pass, "and G-d did not give a command in vain."
Nine are the grades of olive oil (Mishnah, Menachos 8:4).
Nine are the regions of the Land of Israel, for purposes of the Shemittah laws (Mishnah, Shevi'is 9:2).
Nine are the minutes a person should wait between eating, if s/he can't fast on Yom Kippur. (Please consult a rabbi first!)
Nine are the months before a calf is born. (See Sforno's introductory essay to Chumash.)
... is what you get if you add up every three letters of the Alef Beis (for that matter any three numbers according to the numbering of the Alef Beis) if you start from Beis:
2+3+4=9, 5+6+7= 18 and 1+8=9,
8+9+10=27 and 2+7=9, etc.
If you don't believe me figure the rest for yourself!
Nine are the sefiros for which Malchus is the receptor, and the transmitter of their effects to the lower worlds.
Shaarei Orah, Shaar Alef
There are 9 places in Tanach where the letter "ב" comes 3 in a row in the same word.
1 - Melachim2 25:28 - בבבל
2 - Yeshayahu 48:14 - בבבל
3 - Yirmiyahu 29:22 - בבבל
4 - Yirmiyahu 51:44 - בבבל
5 - Yirmiyahu 52:32 - בבבל
6 - Zecharya 2:12 - בבבת
7 - Ezra 5:17 - בבבל
8 - Ezra 6:1 - בבבל
9 - Divrei HaYomim2 36:7 - בבבל