2. It is appropriate for a person to adopt a more stringent approach to
his ritual conduct during the ["Ten Days of Repentance"] than he would
during the rest of the year. [The reason for this is that during this time
period] we are asking G-d to treat us with exceptional kindness
("chassidus" - that is, to go "beyond the letter of the law" and grant us
undeserved mercy) [therefore, we should do the same regarding his
commandments]. For example, a person who eats [kosher] bread baked by a
Gentile baker throughout the year should be careful during these days to
eat only bread baked by a Jew ("Pas Yisroel") (1).
(1) See Kitzur Shulchan Aruch, Chapter 38, for more details about the law
of "Pas Yisroel". If a Jew ignites the oven, for example, the bread is
considered "Pas Yisroel", even though a Gentile did all the baking and
preparation (See Mishna Berura 603:1).