Shavua Tov. A major theme of today's Parsha, is the sanctity of Shabbat. We have a Mitzva at the beginning of ויקהל that tells us that we are to work for six days and rest on Shabbat. We are also not allowed to kindle a fire on Shabbat.
There are many interpretations as to why only this מלאכה out of all 39, is mentioned separately. An accepted explanation is that it actually refers to the high courts being forbidden to give the death penalty of "burning" on Shabbat. And if burning is forbidden, so are the other three methods of capital punishment.
The של״ה הקודש would like us to appreciate the special gift that is Shabbat. In our Shacharit prayers on Shabbat we say ישמח משה במתנת ידו, where Shabbat is referred to as a gift.
The joy felt on Shabbat with our נשמה יתירה, extra soul, is actually one sixtieth of the joy felt in עולם הבא. This explains why we feel sad as Shabbat ends and we no longer feel that bliss.
This is also why our sages say, שקטלה שבת כנגד כל המצוות, that Shabbat is equal to all of the Mitzvot of the Torah.