Sefer HaChinuch ספר החינוך

That the nazirite not enter the tent of a dead body: That the nazirite not enter the tent of a dead body, as it is stated (Numbers 6:6), “to the soul of a dead person he shall not enter.”

I have written what I have known from the roots of distancing impurity from a holy place in this Order in the first commandment (Sefer HaChinukh 362). And it is the same thing and the same reason for the distancing of a holy man from it. And I have also written what I grasped about the reason of the impurity of a dead body in the Order of Emor el HaKohanim (Sefer HaChinukh 563).

From the laws of the commandment — that which they, may their memory be blessed, said (Nazir 43a) that the nazirite is not liable for coming into the tent of a dead body until he goes in completely, and even though he becomes impure regardless from the time when his nose or his toe goes in, it is not called entering until he goes in completely. Therefore a nazirite that goes into a house where there is a dead body inside a chest, a box or a cabinet, and his fellow opens the roof of [the relevant item] with his knowledge, is given two [sets] of lashes, one for “he shall not enter” and one for “he shall not become impure,” as behold the impurity and the entering come at one time; [that] a nazirite that entered a tent of a dead body or a graveyard accidentally and, after it was known to him, remained there enough time to prostrate oneself in the Temple, is liable for lashes; and the rest of its details — are elucidated in Tractate Nazir.

And this prohibition is practiced in every place and at all times by males and females. And one who transgresses it and becomes impure according to the guidelines that we have said is liable for lashes.