When the fourteenth of Nissan falls on the Sabbath, the practices regarding the search for and the destruction of
chametz differ from those observed when this date falls on a weekday, because it is forbidden to search for or burn
chametz on the Sabbath. Instead of the search being held on the night between the 13th and the 14th of Nissan, it is held on Thursday evening, the night between the 12th and the 13th. The
chametz found in the search is burnt on Friday morning, the 13th of Nissan, at the same time as it would be burnt in other years.
The accepted custom is that the entire house is prepared for Pesach on Friday, and the Sabbath meals cooked in Pesachdikke pots and pans and served in Pesachdikke dishes. There is one exception. It is forbidden to eat matzah on the day before Pesach, but we are required to eat bread at our evening and morning Sabbath meals. Therefore, two small challos are eaten at the beginning of both the evening and morning meals. Generally, the practice is to eat them in a place slightly removed from the dinner table so that no crumbs will fall on the Pesachdikke dishes.
We are forbidden to eat chametz after the conclusion of the fourth seasonal hour on Sabbath morning. Hence, we must conclude eating the bread of the morning meal by that time. This may require starting the Sabbath morning services earlier in certain communities. Afterwards, before the conclusion of the fifth seasonal hour, the crumbs and any remaining chametz should be disposed of by flushing it down the toilet or similar means.
In the evening, the preparations for the Seder and the Pesach meal should not begin until the appearance of three stars. Before beginning these preparations, the women must recite the phrase Boruch hamavdil beyn kodesh likodesh (Blessed is He who distinguishes between the holy and the holy).
After this time, and after the recitation of this phrase, the women should light candles.