Chapter 139:14
Chanukah
14. It is forbidden to benefit from the light [of the Chanukah candles] (1)
for the entire time that they are obligated to burn, that is, a half an
hour (2). For this reason, it is customary to place the "shamash," [another
candle used to kindle them,] next to the Chanukah lights. Thus, if one
would perform any activity next to the Chanukah lights, one would be using
the light of the "shamash" (3)
The "shamash" should be placed slightly higher than the other candles, to
make it obvious that it is not one of the [Chanukah] lights.
FOOTNOTES:
(1) For example, one may not eat a meal utilizing their light, nor count or
examine money using their light. There are a number of reasons given for
this prohibition:
a) It should be apparent that the lights are solely for the purpose of the
mitzvah, in order to publicize the miracle.
b) Since the lights commemorate the miracle that occurred with the Golden
Menorah in the Beit Hamikdash (Temple in Jerusalem), we may not benefit
from their light just as one was not permitted to use the lights of the
Menorah in the Beit Hamikdash for any purpose.
c) Using the lights for personal benefit would be a degradation of the
mitzvah ("bizui mitzvah"), because it would appear that one considers the
mitzvah insignificant.
(2) Others are stringent, maintaining that this prohibition applies during
the entire time that they are burning (Mishna Berura 672:8).
(3) It is proper to have another light burning in the room besides the
"shamash" (Ibid.673:17).