Or HaChaim on Numbers 9/אור החיים על במדבר ט׳

1And there were (literally, was) men, etc.: One needs to know why it used the singular form for the many. And also why was it necessary to say, and they could not make the Pesach offering, since it informed us that they were impure. And maybe it is from the angle of that which God commanded on Rosh Chodesh (the first day of the month) about the Pesach offering, as they explained in Pesachim 6a, that the statement (Numbers 9:2), "And the Jews shall make the Pesach offering," was on Rosh Chodesh Nissan. And it would have been proper to guard against impurity [to reach the day of the offering, the fourteenth of Nissan, in a state of purity]. And one might attribute a defect to them that they did not keep the commandment of God and that they became impure and did not concern themselves with the commandment of the Pesach. Hence the verse teaches to say, And there was in the singular form, to say that there was only one matter of impurity by which [all of these] people became impure. And that matter of impurity was not in their power to guard from and they became impure against their will, as per their statement, may their memory be blessed (Sukkah 25a-b). Whether according to Rabbi Yose the Galilean who said that they were the carriers of Yosef's coffin, whether according to Rabbi Akiva or whether according to Rabbi Yitzchak who said they were impure from involvement with a corpse that required burial (met mitsvah), they needed to become impure - even if they knew that their impurity would last through the fourteenth. And this is to what the statement, and they could not make the Pesach offering hints to, saying that they could not guard themselves from impurity to make the Pesach offering. And about its stating, on that day, the rabbis, may their memory be blessed, already made a precise inference (Pesachim 90b) - for one master according to his opinion and for [the other] master according to his opinion. It also wanted to say by using the singular form that it was from the angle of their being individuals that that the could not do the Pesach offering, but if they had been the community, they could have done the Pesach offering, as it can come in impurity [in such circumstances]. Later I saw in the Sifrei of the rabbis, may their memory be blessed, that they made such a precise inference.

1Why should we be diminished, etc.: One needs to know the claim of the people in their statement, "why should we be diminished." Is the reason not answered by their own mouths - "we are impure"? And what do they want given to them - a new Torah? And maybe it is from the angle that they became impure with His consent, may He be blessed. Whether according to the opinion that they became impure from a corpse requiring burial or whether according to the opinion that they carried the coffin of Yosef, they thought that God would judge them as if they were pure, and in the same way that we find (Pesachim 77a) that God accepts the Pesach offering of the community when it is impure. And for this [reason], they claimed, "why should we be diminished" - and just because they preformed a commandment, they should be diminished from the Pesach offering? Or they meant to say that they be able to make up for the Pesach offering, like with the festive (chagigah) offering, about which they said (Chagigah 9a), "celebrate (chagog) the holiday through the whole festival." So too, God should command them that they be able to make up for the Pesach offering the next day, and that is the [meaning of the] statement, in its time, which is the time of the Pesach offering. And maybe for this [reason], the [previous] verse was exact to say on that day: According to the opinion that says that it was the seventh (last) day of their impurity, the explanation is that for this reason did they come on that day - so that he would say to them to make it up on the next day. And in this way, we gain the explanation [of something else]: God said this commandment of Pesach Sheni (the second Passover) after these men asked - to say that even if they will be pure during the days of Pesach, like in our case; nonetheless, he does not make it up during the seven days of Pesach like the festive offering, but rather on the second (next) month. It also means by saying, why should we be diminished, etc.: that since it was the seventh day of their impurity, that they were claiming that their Pesach offerings could be slaughtered for them; in the [same] way as we slaughter, and sprinkle [from, the offering] of one impurified by creeping animals (sherets) - since they will become pure at night and they only have [remaining] impurity on that day. And that is the [meaning of the] statement, in its time. And the rabbis, of blessed memory, said other matters - 'and these and those are the words of the living God.'