According to the Tanchuma (Parshas
Nasso 29) It is forbidden to make any use of the oil that is left over from
the Chanukah candles because it was designated for a mitzvah. Therefore, it
should be discarded by burning it up separately. A person shouldn’t say I am
not going to fulfill the mitzvos of the Elders since they are not from the
Torah. G-d says to him, My son, you are not permitted to say that. You should
do everything they ordained…for I agree to all their decisions.
It is forbidden to derive benefit from form the oil
or the wicks of the Chanukah candles even if they went out only after they had
burned the full time required to fulfill the mitzvah. This prohibition applies
not only the one candle that is required to fulfill the mitzvah, but also the
additional candles we light as hidur mitzvah, for they, too, have been
set apart to be used in the performance of the mitzvah.
Oil that remains in the bottle is not prohibited
even though the oil that was used in the menorah was taken from it.
Oil that is left over from the Chanukah candles
should not be saved to be used the following year. Since it is forbidden to
derive benefit from it, we are afraid that it will be used, if only
accidentally. Even if it is stored in a container which is repellent, it may
not be saved.
Using something to do a mitzvah is not considered
getting benefit from it, but we light Shabbos candles in order to benefit from
them. Therefore, It is forbidden to use the oil that is left over from the
Chanukah candles for Shabbos candles. For the same reason, it is forbidden to
use oil that is Orlah for Shabbos candles.
If oil that is left over from the Chanukah candles
mixes with other oil, it may be used if there are sixty parts of the permitted
oil against one part of the forbidden oil. If there are fewer than sixty parts
of permitted oil, there is disagreement among the poskim whether it is
permitted to add permitted oil to the mixture. In practice, the later poskim
are machmir.
It is important, when burning the oil and wicks that
are left over from the Chanukah candles not to touch them with a knife or
fork, for they will absorb the prohibited oil. It that happens, they can be
kashered by hagala. Libun is not necessary.
Oil that remains from Shabbos candles after they
have gone out may be used for any purpose. When oil remains from a yarzeit
candle after it has gone out we are careful not to use it. According to the
book of the customs of the Jewish community in Worms by Rav Yuzpa Shamash part
two, page 249, a wax candle that has once been lit in a synagogue may be lit
only in a synagogue, for we enhance but do not diminish kedushah. The remains
of a yahrzeit candle may not be used for the same reason.