It is a mitzvah to start each of the Shabbos meals – the third meal as well
– with two whole loaves of bread. The two loaves (lechem mishnah) commemorate
the double portion of manna that was collected on erev Shabbos while the Jews
wandered in the desert after the Exodus, as it is written, “Gather lechem mishnah…”
The mitzvah of lechem mishnah applies to both men and women, as women
also participated in the miracle of lechem mishnah.
The mitzvah of lechem mishnah applies to Yom Tov as well as Shabbos.
A person fulfils the mitzvah of lechem mishnah when the person who
is making the blessing over the bread for those partaking in the meal has two
loaves before him. Even if a person has not yet washed when the host makes the
blessing, he fulfills the mitzvah of starting his meal with lechem mishnah,
for the washing of hands before eating bread is not considered a distraction from
eating. Even though he washes and starts eating after his host, it is considered,
for the purposes of the mitzvah of lechem mishnah, as though he started
his meal with his host.
The mitzvah of lechem mishnah applies to every time a person eats on
Shabbos – no matter how many times – if his intention is to sit down to a proper
meal. Otherwise, it is not necessary.
Several people in turn can make the blessing over bread on the same two loaves,
even though each one will have to wait until the others have said the blessing
before eating. The delay does not separate the blessing from the actual eating
and invalidate it so long as the person does not focus his mind on other matters.
After hearing the blessing over bread made by other participants in the meal,
a person should not say amen. If he does, he should not recite the blessing himself.
The poskim are divided on the question as to whether, in such a case, the blessing
should be recited, and when the obligation to recite a blessing is not clear,
we refrain from saying it. But if he answers amen to a different blessing, it
invalidates the blessing he recited and must recite the blessing again.