This sugya discusses the prohibition of Bal Tosif – adding to those commandments that were given on Har Sinai. There are several sources for this issur, and they are found throughout Sefer Devarim – which is leined over the summer. We discuss the nuances behind each specific Pasuk, and why there is a need for multiple sources.  We also discuss why the Chachomim were permitted to add to “existing” Mitzvos (i.e. adding extra Tekios on Rosh Hashana, including poultry in the prohibition of Bassar B’chalav, etc.) or institute completely new Mitzvos (i.e. Netilas Yadayim, the Yomim Tovim of Chanukah and Purim and their associated Mitzvos).