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 is this year! (לפ"ק)
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
9 - is the number of Parah Adumahs that have existed-- and utilized for ritual purposes-- thus far in Jewish history.
The mishna in Maseches Parah 3:5 lists these 9 Parah Adumahs:
3) שִׁמְעוֹן הַצַּדִּיק (did 2)
5) וְיוֹחָנָן כֹּהֵן גָּדוֹל (did 2)
7) אֶלְיְהוֹעֵינַי בֶּן הַקּוֹף
8) וַחֲנַמְאֵל הַמִּצְרִי
9) וְיִשְׁמָעֵאל בֶּן פִּיאָבִי
The Rambam in Hilchos Parah Adumah 3:4 codifies this number...
וְתֵשַׁע פָּרוֹת אֲדֻמּוֹת נַעֲשׂוּ מִשֶּׁנִּצְטַוּוּ בְּמִצְוָה זוֹ עַד שֶׁחָרַב הַבַּיִת בַּשְּׁנִיָּה. רִאשׁוֹנָה עָשָׂה משֶׁה רַבֵּנוּ. שְׁנִיָּה עָשָׂה עֶזְרָא. וְשֶׁבַע מֵעֶזְרָא עַד חֻרְבַּן הַבַּיִת
Nine red heifers [existed] from the time that we were commanded to fulfill this mitzvah until the destruction of the second Beis Hamikdash. The first parah adumah was done Moshe Rabeinu. The second was done by Ezra. Seven more parah adumahs [existed] from Ezra until the destruction of the second Beis Hamikdash.
... before concluding that IH one day, b'mheirah b'yameinu:
וְהָעֲשִׂירִית יַעֲשֶׂה הַמֶּלֶךְ הַמָּשִׁיחַ מְהֵרָה יִגָּלֶה אָמֵן כֵּן יְהִי רָצוֹן:
And the tenth will be prepared by the Melech HaMashiach; may he speedily redeem us. Amen, may it be G‑d's will.
R’ Yona (Shaarei Teshuva 3:178-186.) lists nine different categories of lies. In order of severity, they are:
a. People who cheat in business, causing others financial loss;
b. People who exploit others after gaining their trust through deception;
c. People whose lies cause others to lose out on some gain or benefit that was coming to them;
d. People who fabricate stories merely for the sake of lying;
e. People who hold out the promise of giving another person material goods while never intending to follow up on their promise;
f. People who intend to keep a promise but do not honor their commitment;
g. People who act as though they did a favor or a good deed for another;
h. People who praise themselves for virtues that they do not possess;
i. People who change minor details when retelling an episode.