Why is a Nazir not permitted to perform the Mitzvah of burying his deceased relatives?
Seforno: Because it is not correct for him to defile his Kedushah
for the sake of a dead person.
Seforno: Which is on a par with that of a Kohen Gadol.
Seforno: In similar vein to the Yerushalmi in Pesachim, 3:7 'Is it because there is a shortage of graves in Teverya, that I sent you to Netzivin (to bury the dead there?! I sent you to learn Torah!)'