בנין אב

This Shabbat is special as we Bench Rosh Chodesh, finish the Book of Shemot, and read from a second Torah, פרשת החודש. We also have a double Parsha of ויקהל-פקודי.

Parshat ויקהל begins with an account of how Moshe gathered the entire congregation of Israel the day after Yom Kippur, and reiterated the importance of Shabbat.

The point that is most noticeable, is that Moshe instructs the people not to kindle a fire on Shabbat. Some want to learn the principle of בנין אב, from this instruction. The kindling of a fire is the precedent setting case for the other thirty-eight מלאכות of Shabbat.

We find this idea of בנין אב in many instances in the Torah. The precedent setting case, becomes the rule for all other cases that are in the same category.

This בנין אב concept is among the list of the thirteen methods of derivation presented by רבי ישמעאל, that we read every morning before פסוקי דזימרה.