As we have seen, the last Mishna (49b) teaches that there are many different cases where a nazir who becomes tameh met will be forced to conclude his nezirut by cutting his hair and undergoing the process of tahara – purification – after which he will begin his nezirut again from the beginning.
Our Gemara notes that the Mishna repeats the statement al elu aha-nazir megale’ah, “In these situations the nazir will have to shave,” twice, and suggests that the first statement comes to exclude the case of an etzem ke-se’orah – a situation where the only part of the dead body is a bone the size of a barley grain. In such a situation, only actual physical contact with the bone or actually carrying the bone will lead to tum’ah severe enough to force the nazir to shave. If, however, the nazir walked into a house in which such a bone was present – a situation of tum’at ohel that usually would create a situation of ritual defilement – the nazir would not become tameh.
The second statement of al elu aha-nazir megale’ah is understood to exclude the case of even ha-sekhukhit.
Although the term sekhukhit is usually understood to be another version of the word zekhukhit – glass – in our case it appears to be related to the words sikukh and kisuy – meaning “covering” – and to refer to a stone that is held over the body as a type of tent.
Rashi offers two other suggestions, either that it refers to an even misma – a heavy rock that is placed on the dead body, which would not transfer tum’ah to the nazir even if he sits on it, or else it is a rock that is carried by the nazir on his back that passes over a dead body.