Chapter 90:22 & 23
22. If possible, a Gentile who purchased merchandise from a Jew should be
prevented from collecting it on Shabbos (1).
23. A person who has a "yahrtzeit" (2) on Shabbos and forgot to light a
candle for this purpose, is permitted to tell a Gentile during "bein
hash'moshos" (between sunset and the appearance of three stars on Friday
evening) (3), to light it for him (4). On Shabbos itself, however, it is
forbidden [to ask a Gentile to light the candle].
(1) The reason the Sages didn't want the Gentile to collect the goods on
Shabbos is because onlookers might think that the Gentile is transporting
goods for the Jew (Shulchan Aruch 246:2) or that the Jew actually sold him
the goods on Shabbos.
(2) Anniversary of the death of one's parent.
(3) During that period of time, we refrain from doing activities which are
prohibited on Shabbos, due to our inability to determine the precise moment
that "night" (and therefore, shabbos), begins.
(4) Due to the indeterminate status of the "bein hash'mashos" period,
certain leniencies apply with regards to the rabbinical prohibition of
instructing a Gentile to perform forbidden activities (See Shulchan Aruch
261:1). It is permissible to ask a Gentile during "bein hash'mashos" to
perform any forbidden activity (whether Biblical or rabbinical) for any one
of the following reasons:
a) Shabbos needs
b) To prevent substantial financial loss
c) A Yahrtzeit candle
d) For the sake of a mitzvah