After Kiddush is recited at the Seder, everybody washes hands as we do before eating bread, washing each hand three times consecutively. Even though the Matza will be eaten only much later, washing is required before eating Karpas the vegetable dipped in saltwater. One does not, however, recite the Beracha of "Al Netilat Yadayim" over this washing. Chacham Ovadia Yosef rules in his work Chazon Ovadia (p. 32) that one should not speak after washing his hands until after he partakes of the Karpas.
Two reasons are given for the requirement to eat Karpas at the Seder. Firstly, the word "Karpas" consists of the same letters as the word "Perech" slave labor and the letter "Samech," which has the numerical value of sixty and thus alludes to the sixty ten thousands or 600,000 Jewish slaves in Egypt. Secondly, eating Karpas dipped in salt water is intended to arouse the children's curiosity so that they will remain awake and be involved in the Seder.
Our practice is to use specifically celery for Karpas.
Should one perform Heseiba reclining while eating Karpas?
This issue is subject to debate among the Halachic authorities. The Shibolei Ha'leket (Rabbi Tzidkiya Ben Avraham, Italy, 1230-1300) held that one should not eat the Karpas while reclining, since it commemorates the slave labor performed by our ancestors in Egypt, and does not express the theme of freedom and royalty. By contrast, the Abudarham (Rabbi David Abudarham of Seville, Spain, 14th century) maintained that one should, in fact, recline while eating Karpas, as yet another means of arousing the children's curiosity. Rabbi Chayim Palachi (Turkey, 1788-1868), in his work Chayim La'rosh, ruled that one should endeavor to satisfy both views by eating some Karpas while reclining and some while sitting upright.
As for the final Halacha, Chacham Ovadia Yosef writes that it is preferable for one not to recline while partaking of the Karpas, but those who wish may recline or follow Rabbi Palachi's view to eat some Karpas in both positions.
There is some question as to whether one must recite a Beracha Acharona after eating the Karpas, and it is therefore advisable to partake of less than a Ke'zayit (approx. 30 grams) of Karpas, so that according to all views a Beracha Acharona will not be required. Chacham Ovadia Yosef writes that one should preferably eat less than 18 grams of Karpas. Nevertheless, if a person ate a larger amount of Karpas he does not recite a Beracha Achaona.
It is preferable for the person leading the Seder to recite the Beracha of "Borei Peri Ha'adama" over the Karpas on behalf of everybody at the Seder, given the rule of "Be'rov Am Hadrat Melech," that public performance of Mitzvot brings greater glory to God. The person reciting the Beracha should have in mind that he recites this Beracha on behalf of both himself and the others, and they, too, must have in mind to fulfill their obligation through his recitation. They should answer "Amen" to his Beracha, but must ensure not to answer "Baruch Hu U'varuch Shemo." If, however, the person leading the Seder does not pronounce the words properly and clearly when reciting the Beracha, then the others should each recite the Beracha personally, rather than fulfill the obligation by listening to the leader's recitation.
When reciting the Beracha over Karpas, one should have in mind for the Beracha to apply as well to the Marror, which is also a vegetable and is eaten at a later point in the Seder.
The Ben Ish Chai (Rabbi Yosef Chayim of Baghdad, 1833-1909), in Parashat Tzav, writes that according to Kabbalistic teaching one must ensure to leave the Karpas on the Seder plate even after he partakes of his portion of Karpas. Rather than clear the Karpas off the table, one should leave the Karpas on the Seder plate at the table throughout the entire Seder. An allusion for this Halacha is found in the verse (Tehillim 26:6), "Erchatz Be'nikayon Kapai Va'asoveva Et Mizbachacha Hashem" ("I shall wash my hands clean and surround Your altar, God"). The word "Mizbachacha" may be read as an acronym for the words Matza/Marror, Zero'a (the shank-bone), Beitza (the egg), Chazeret/Charoset, and Karpas. This verse thus implies that all these items must be present on the "altar," referring to the Seder table.
Summary: One washes before Karpas as he does before bread, though without a Beracha, and should not speak until after eating the Karpas. It is preferable not to lean when eating Karpas. Ideally, the one leading the Seder should recite the Beracha over the Karpas on behalf of everybody else, who answers "Amen" to his recitation. One should preferably eat less than 18 grams of Karpas. The Karpas should remain on the Seder plate throughout the entire Seder.
