One takes the karpas and dips it in vinegar or in the haroset in order to kill the worms that are sometimes found in the vegetables. One then recites the blessing borei peri ha-adamah. Rabbeinu Tam and Rashbam instructed their students to do the first dipping in vinegar. This was based on the statement in the Mishnah, "They then set it before him. He dips the lettuce before he has reached the after course of bread. They set before him matzah, lettuce (hazeret) and haroset, and two side dishes, even though haroset is not compulsory." (Mishnah Pesahim 10:2) The Mishnah does not mention haroset until the second dipping, proving that we do not dip in the haroset for the first dipping. Rabbeinu Yona explains that the first dipping is not considered obligatory. Rather it is performed as a way of calling attention to the Seder. Since we do not dip vegetables in haroset all year long, the reason for this practice cannot be to prevent kafa. Therefore it is not our custom to eat the lettuce (hazeret) without haroset, as we do all year long. Since the second dipping is regarded as a mitzvah, the sages were more careful in its performance. Hai Gaon explains that kafa is Aramaic from the word kafui (coagulation); it refers to a gaseousness which strikes the intestines from certain types of food. Haroset is a type of medicine which prevents the gaseousness. We do not recite a blessing for haroset even though it is considered a commandment, because haroset is secondary to the primary food, the lettuce or the maror. We learn, "Any time we have two foods, we recite the blessing on the primary food and not the secondary food. We recite al achilat maror and not borai peri ha-adamah for the second dipping since we already recited this blessing earlier in the Seder and the reading of the Haggadah is not considered to be an interruption between the two acts.

However it is necessary to recite the blessing for the washing of the hands again because it is considered an interruption for the washing and his hands may have inadvertently touched something impure. It is not necessary to recite the concluding blessing borei nefashot for the karpas since the reading of the Haggadah is not considered an interruption. It is also not necessary after eating the maror to recite this blessing since the commandment is to eat the matzah and the maror together, as scripture, "Matzah and maror they shall eat it." It is considered to be part of the meal, and it is not necessary to recite borei peri ha-adamah again during the meal. The vegetables which we dip at the beginning of the Seder are meant to make the children curious since we normally don’t dip vegetables prior to the meal. If one does not have other vegetables - and only has maror - should begin the Seder by reciting two blessings, al achilat maror and borei peri ha-adamah when he eats and dips the maror in place of the karpas. He should then dip it in the haroset and eat an olives size of it. When he completes the reading of the Haggadah and recites the blessing over the matzah, he should eat the maror again, this time without a blessing.