As we learned on yesterday’s daf, although a kohen gadol and a nazir are prohibited from coming into contact with a dead body, both of them will be obligated to deal with a met mitzva (a situation where no one is available to bury a dead person). In examining the source for this halakha, our Gemara quotes a baraita that describes how a person who is on his way to bring his Passover sacrifice or to perform a brit on his son will go to perform these mitzvot even if he hears that a close relative has died; nevertheless, if he comes across a met mitzva he is obligated to stop and take care of the burial, even at the expense of missing these important commandments.
The mitzvot of korban Pesaḥ and brit milah are unique among positive commandments, as they are the only ones that are considered so central to Jewish life – both of them represent joining the Jewish community – that someone who does not perform them is liable to receive the punishment of karet . Rashi notes that the story presented in the baraita may be describing one person who is on his way to perform both of these mitzvot, since a person cannot bring a korban Pesaḥ unless all members of his family are circumcised. Rabbeinu Peretz points out that even though a father can circumcise his son while he is in a state of tumah, still we can derive an important lesson from this ruling. The baraita is teaching that a person is obligated to postpone the required brit milah and spend as much time as is needed for the burial preparations for the met mitzva.
Some of the commentaries assume that the baraita is discussing a nazir who was on his way to bring the korban Pesaḥ and perform the brit milah; others suggest that the baraita could be referring to anyone, but the message of the centrality of taking care of the needs of the met mitzva remains applicable in all cases.