What Happens if You Leave Your Sefer Open?

In the sefer "Kitzur Shala"h," the author brings the following story:
"A certain scribe completed his work for the night and left the scroll open to the verse [that he had just finished writing] '...and the goats will dance there.' (ישעיה יג, כא) Upon arising early the next morning before daybreak, he encountered a demon sitting on his chair. The demon told him 'know that I am the demon named שד - the Guardian of the Pages and I have come to harm you. Yet, I will forgive you for I heard during the ten days of penitence that I do not have permission to harm you. Instead, accept upon yourself not to write further until such a time.' And so he did."
R. Chaim Palagi writes that the reason R. Shimon bar Tzemach Duran (the Tashba"tz) merited to have his teshuvos printed in such a beautiful manner (large size and good binding) more than the other books of his days was because he was always careful to spread an honorable cloth over the open books he was learning from.
קיצור של"ה מסכת שבועות עניני לימוד הנערים
יפה ללב ח"ג (חיו"ד) סי' עז"ר סק"ג
ועי' בספרו רוח חיים ח"א סי' עז"ר
See here, and here

Don't Leave Your Sefer Open

When one learns Torah from a sefer and they wish to get up and take a break, they should not leave the sefer open. In fact, the Sha"ch writes that "It's known to the scholars of truth that there is a certain angel named ש"ד which stands for שומר דפים - Guardian of the Pages. [This angel] ensures that he who walks away from an open sefer will forget his studies."
R. Moshe Chagiz, author of Mishnas Chachamim (brother-in-law of the "Pri Chadash") writes that he heard that the "true scholar" R. Chaim Benveniste (author of the "Kneses Hagedolah") had a silk cloth that he would use to cover the seforim he was learning from when he would walk away from them. Because he was so busy, he did not have time to close them and find his place again, so he used this method.
ש"ך יו"ד סי' רע"ז סק"א
משנת חכמים סי' ר"י
ועי' ספר חסידים סי' תתקי"ח
See here

Who's "Zevad-yah?"

Following the completion of hallel on Rosh Chodesh, many have the custom to recite the passuk "ואברהם זקן בא בימים..." followed by the mention of "Zevad-yah," that He should guard us and give us life, etc.
Where does this come from and who is "Zevad-yah?"
R. Avraham Dovid Lavat in his book "Sha'ar Hakollel" (סי' ל"ז סק"ט-י) says that this is not found in any of the works of the Ariza"l, and for this reason, the Alter Rebbe in Siddur writes that "there are those accustomed to saying the following."
Where does it indeed originate?
R. Emanuel Chai Riki, a late seventeenth century Kabbalist, authored a sefer on kabbalah entitled "Mishnas Chassidim." There he writes that if one wishes long life, they should say the above mentioned passuk after hallel. He continues to explain that the first letter of each of the words of this passuk spell out a unique name of Hashem - "זבדי-ה": The ז of זקן, the ב of בא, the מ of the word בימים is switched with the letter ד (according to the cheshbon of איק, בכר), and the final two letters "י-ה" from Hashem's name mentioned next in the passuk.
He concludes that the name should be pronounced "Zevud-yah" - with a קמץ under the ב. The spelling with a פתח appears as a man's name in עזרא ח, ח.
משנת חסידים מסכת ראש חודש פ"ב מ"ו-ז
ויש אומרים שהוא שם מלאך, עי' שער הכולל שם ובספר כף החיים סי' ה' סק"י בשם האריז"ל
See here

Pose Your Own Questions

One of the most important aspects in the development of halachah as we know it is the famed "שו"ת" - the "Responsa." Throughout the ages, Jews have been sending in questions to their Rabbis and receiving answers, expanding and formulating the scope of Jewish law.
What if you're a Rabbi and wish to share a thought, but did not yet receive the letter in the mail prompting you to reply - how would you teach the world your ideas?
Well, you can compose your own "questions." R. Yisroel Isserlan was a Rabbi who wrote many teshuvos, collected in the sefer "שו"ת תרומת הדשן". His voluminous work serves as an important source for Ashkenazi law, oft quoted by the Rema in Shulchan Aruch, and indeed, he authored many of his own questions.
Knowing that, the Sha"ch rules that any ideas that could be gleaned from his questions have halachic force. In fact, if the question implicates a stringency over the answer, we follow the chumrah of the question.
ש"ך יו"ד סי' קצ"ו סק"כ