Shulchan Arukh Orach Chayim · Siman 471

English

On Passover Eve After the Tenth Hour It Is Forbidden to Eat Bread. Containing 3 paragraphs: It is forbidden to eat bread from the tenth hour onward, so that one will eat matzah with appetite. However, one may eat a small amount of fruit or vegetables, but should not fill his stomach with them. (And if he is sensitive such that even eating a little harms his appetite, everything is forbidden.) (Rabbeinu Yerocham) One should not drink a small amount of wine, because it satiates, but if he wishes to drink a large amount of wine, he may drink, because when he drinks a lot it stimulates the appetite for food.

English

And before the tenth hour, it is permitted to eat egg matzah. Gloss: But matzah with which one fulfills the obligation at night is forbidden to eat all day on the fourteenth (Ran, chapter Elu Ovrin, in the name of the Rambam and the Maggid, chapter 6). A minor who does not know what is told at night about the Exodus from Egypt may be fed [matzah] (Terumas HaDeshen, section 7). Some have the custom not to eat lettuce on the eve of Passover in order to eat the bitter herbs with appetite (Tashbetz 455, section 3). Similarly, on the first day of Passover [they refrain from lettuce] in order to eat it on the second night with appetite. Similarly, some have the custom to minimize eating matzah on the first day for this reason (Kol Bo). Some are even more stringent not to eat fruits in order to eat the charoset with appetite, but one need not be concerned with that custom. Some are stringent not to crumble or break the matzos on the eve of Passover so as not to come to eat from them (Mahariv)

English

If one began to eat before the tenth hour and his meal extended into the night, his law is like on Sabbaths and other festivals as explained in Section 271:6. (And it is a mitzvah to wash and shave on the eve of the festival and to wear nice clothing as on Shabbat, and see above Sections 260 and 262).