1) REMOVING OIL FROM A LAMP ON SHABBOS
QUESTION: The Gemara cites the Mishnah in Shabbos (29b) that states that according to the Chachamim, one may not place, on Erev Shabbos, a reed (or other receptacle that contains oil) with a hole in it above a burning flame so that the oil will drip into the lamp on Shabbos. The Chachamim were concerned that one might be tempted to take oil from the container on Shabbos and thereby transgress an Isur d'Oraisa. What Melachah will he perform if he removes oil from the container? RASHI explains that he will perform the Melachah of Mechabeh, extinguishing a flame.
How does one extinguish the flame in the lamp by removing oil from the container that drips into the lamp? Although he indirectly causes the flame in the lamp to go out sooner, this is considered "Geram Kibuy" and should not be prohibited, because we rule like the Rabanan (Shabbos 120a) who permit Geram Kibuy! (ROSH, Beitzah 2:17)
(a) The ROSH answers that the act of removing oil from the container is more severe than other acts of Geram Kibuy. In a normal case of Geram Kibuy, one places earthenware pots full of water around a fire so that the water will extinguish the fire when the pots burst (see Shabbos 120a-120b). This form of Geram Kibuy is permitted. In contrast, when one removes oil so that it does not drip into the lamp, one causes the fire to go out in a more direct way -- by removing its fuel, the oil. Removal of the fire's fuel is a more direct act of extinguishing than placing something in the fire's path which will eventually extinguish the fire. Therefore, this act is forbidden because of Mechabeh, even though it merely causes the fire to go out sooner.
(b) TOSFOS in Beitzah (22a, DH veha'Mistapek) does not accept this logic. Tosfos maintains that one who removes oil from an oil lamp is not Chayav for Mechabeh, because the removal of the fuel of a fire is a normal act of Geram Kibuy and is permitted. For this reason, Tosfos permits cutting (with a flame, so as not to make a Kli) the bottom half of a candle that is lit, even though doing so removes the flame's fuel. Why, then, may one not remove oil from an oil lamp? Tosfos explains that at the very moment that one removes oil from a lamp that is burning, the flame becomes smaller or weaker. Making the fire smaller or weaker is an act of Mechabeh.
According to Tosfos, why should removing oil from the container that drips into the lamp be forbidden? The container itself is not burning; it merely holds the oil which drips into the lamp that is burning. How can removing some of the oil possibly affect the fire?
The TIFERES SHMUEL (on the Rosh in Beitzah) explains that according to Tosfos, the fear is that one will remove all of the oil from the receptacle. By removing all of the oil, it will immediately stop dripping into the lamp, and thus the flame will be affected immediately.
However, this answer is difficult to understand, because even when one removes all of the oil, one does not weaken the flame itself. One merely prevents the oil from being added to the lamp to strengthen the flame. Stopping the drip does not lessen the existing fire in any measure.
Perhaps Tosfos maintains that the Gemara refers to a case in which the oil in the receptacle drips directly into the oil lamp in such a way that there is a steady stream of oil (or an elongated drop of oil) from the receptacle into the lamp. When one removes oil, it is possible that he might draw back that stream of oil minutely and lessen the amount of oil supplied to the flame in the lamp. This effectively would be the same as removing oil directly from the oil lamp itself, which, according to Tosfos, causes the flame to weaken.