Or HaChaim on Exodus 12:4/אור החיים על שמות י״ב:ד׳

1 ואם ימעט הבית, If the household be too small, etc. This verse can be explained satisfactorily both according to the view of Rabbi Yossi and the view of Rabbi Yehudah who have conflicting views reported in Pessachim 99 in a situation where the two lambs of two different families have become mixed up and the members of the respective families are not sure to which animal they belong. According to Rabbi Yehudah it is sufficient if one member of each family partakes of both animals in order to fulfil the condition laid down in our verse, i.e. if the number of people originally designated to eat from one lamb had somehow shrunk. Rabbi Yehudah considers the operative part of the verse אם ימעט הבית מהיות משה as the diminutive word ימעט, reduced number, but not total absence. Rabbi Yossi holds that as long as either one of the two animals is not temporarily without anyone committed to eat from it, neither one is disqualified. Rabbi Yossi pays especial attention to the words מהיות משה, i.e. to leave that lamb as temporarily not belonging to anyone.

2The verse may also tell us that the lamb must be big enough to provide a minimum of an olive size's amount of meat for every member of that household.

3The verse may also be understood as a blessing. If someone has a large family and the family cannot afford much, the lamb will nevertheless provide an adequate amount of meat for every member thereof because consumption of the meat is for the sake of fulfilling G'd's commandment.

4לפי אכלו תכסו על השה, "according to every man's eating you shall make your count for the lamb." According to Pessachim 88 this means that a father may slaughter the Passover lamb on behalf of his wife and his children who are minors without having to consult them first. Pessachim 87 also teaches that a married woman who was still in the habit of frequenting her father's home, and who finds that both her husband and her father have included her as potential participants in their respective Passover offerings, has the choice to decide to which household she wishes to belong for the purpose of consuming the Passover. This is based on the words לפי אכלו meaning "according to where she is in the habit of taking her meals."

5Another rule we learn from this verse (Pessachim 90) is that a person who is obligated to bury a near relative maybe included in the count for a Passover lamb though at the time the lamb is being slaughtered he is not yet under an obligation to fulfil this commandment due to his prior obligation to attend to the burial. The operative word is לפי אכלו meaning that as long as he is fit to eat it in the evening.

6The same word also serves as a ruling concerning a person afflicted with a discharge from his sexual organ (זב). The Passover may be slaughtered on such a person's behalf. The same applies to a person who is in the process of undergoing ritual purification and only needs to await sunset on that day to have completed this process. In all these instances the deciding factor is whether the person in question will be legally entitled to partake of the Passover on the evening of the 15th of Nissan.

7Both Mechilta and Pessachim 90 consider Numbers 9,6 in which Israelites are complaining about not being able to eat of the Passover in the desert due to their being ritually impure, as referring to people who would have completed their purification process by the evening of the 15th of Nissan. Why were these people prevented from eating the Passover then? The reason was that their ritual impurity was of the most severe kind, i.e. due to contact with the dead. According to one authority such impurity is still considered as sufficiently effective even if the party concerned has already undergone the final sprinkling of spring water. According to Rabbi Yossi we could conclude that even a person who was on the last day of purification after having been in contact with a corpse would qualify to join a household whose head had included him in the Passover guests at the time he slaughtered his animal. This is especially so if the person had already undergone immersion in a ritual bath.