- מאכל בן דרוסאי
The Mishnah at the bottom of 19b stated that one may not roast meat, onions or eggs erev Shabbos unless there is enough time for them to “become roasted” before Shabbos.
R’ Elazar said in the name of Rav that the Mishnah means that there must be enough time for the food to become roasted as the food of Ben Derusai (מאכל בן דרוסאי) .
Ben Derusai was a bandit that would cook his food one-third the normal time. (Rashi)
- Lighting the fire in the Beis Hamoked erev Shabbos
Rav Chisda explains that we learn from the passuk לא תבערו אש בכל משבתיכם ביום השבת – You shall not kindle fire in any of your dwellings on the Sabbath day, that it is forbidden to ignite a fire in "מושבתיכם" which means anywhere outside of the Beis Hamikdash, as opposed to the burning of sacrificial parts and fats on the mizbeach (the Temple Altar), which is permitted.
However, this exemption of igniting a fire on Shabbos only applies to the korbonos which is so to speak for Hashem, and does not apply to kindling the pyre in the Beis Hamoked ( the Fire Chamber), being that the fire is there only for the use of man.
The reason why lighting the pyre in the Beis Hamoked was permitted before Shabbos and there was no concern that one might come to stoke the fire after nightfall is that the Kohanim are conscientious (כהנים זריזין הן), and they’ll ensure no one comes to stoke it.
- Wicks and fuels
The opening Mishnah of the second perek identifies wicks that may not be used for Shabbos lights because they do not hold the flame well, and fuels that are prohibited to be used because they are not easily drawn into the wick.
