Ketev Meriri – The Demon
This Demon is mentioned in Torah, Halacha and Midrash and is in control during the “Three Weeks” From 17th of Tamuz to the 9th of Av (July).
Pesachim 111 - There are two Shedim called Ketev - one [is found] before noon and one after noon;
1. The one before noon is called Ketev Meriri, and it appears in jars of Kutach, and revolves on a mixing spoon (Rashi Devarim 32:24 - the name of the Shed is Meriri; Ketev means 'cutting'); 2. The one after noon is called Ketev Yashud Tzaharayim, and it appears in goats' horns, and revolves in a sieve.
Abaye was walking; Rav Papa was on his right and Rav Huna brei d'Rav Yehoshua was on his left. He saw Ketev Meriri approaching him on his left - he had Rav Papa and Rav Huna switch sides.
Rav Papa: Why aren't you concerned for me? Abaye: Your Mazel is good now (you are wealthy).
From the first of Tamuz until the 16th it (Ketev Meriri) is common; afterwards, it is doubtful if it is common; it is found in the shadow of Chatzva (a shrub) less than an Amah tall, and in morning and afternoon shadows less than an Amah, and primarily in the shadow of an outhouse.
During these 3 weeks you must be careful not walk alone from the 4th until the 9th hour; be extra careful in the afternoons, not to walk between shadow and sun light, do not use force to discipling kids (no spanking),
בספר דברים לב, פסוק כד: מְזֵי רָעָב וּלְחֻמֵי רֶשֶׁף וְקֶטֶב מְרִירִי, וְשֶׁן-בְּהֵמֹת אֲשַׁלַּח-בָּם, עִם-חֲמַת זֹחֲלֵי עָפָר.
מדבר באופל יהלוך מקטב ישוד צהרים
יגאלהו חשך וצלמות תשכן עליו עננה יבעתהו כמרירי יום
השקד הזה הוא משעת חניטתו עד גמר בישולו עשרים ואחד יום כמנין ימים שבין שבעה עשר בתמוז שבו הובקעה העיר לתשעה באב שבו נשרף הבית