A fence around the law – Korach
Towards the end of the sidra comes a grave warning to Aaron and his tribe that they “bear the iniquity of the sanctuary” if any unauthorised person enters the sanctuary or touches the holy objects.
Why blame Aaron if an Israelite gets into the sanctuary unlawfully? Surely it is the Israelite who is at fault, not Aaron!
But the high priest has overall charge of the security of the tabernacle, and if an unauthorised person gets in it reflects on Aaron and the efficiency of the kohanim.
In Judaism it is not only the sanctuary that has to be protected from intrusion. The Torah too is accorded a security system by means of precautionary measures known as fences around the law.
If a house is to be kept intact it needs a fence; if the Torah is not to be intruded upon it needs precautionary measures. Hence for instance the practice of beginning Shabbat earlier than sunset and ending it later than nightfall the following day.
The extension of time at each end protects Shabbat and keeps it holy.