Bal Tosif

There is a negative mitzvah not to add onto the mitzvot of the Torah as it says in the pasuk "אֵת כָּל־הַדָּבָר אֲשֶׁר אָנֹכִי מְצַוֶּה אֶתְכֶם אֹתוֹ תִשְׁמְרוּ לַעֲשׂוֹת לֹא־תֹסֵף עָלָיו וְלֹא תִגְרַע מִמֶּנּוּ".

Nature of the Prohibition

1. Some say that the prohibition means that one may not permanently establish a new mitzvah. Some say that it a Bet Din declares that a rabbinic prohibition is actually a Biblical one they are in violation of Baal Tosif. Others disagree.
2. Some say that the prohibition includes fulfilling a mitzvah in an expanded or enlarged manner.
   1. For example, fulfilling the mitzvah of Daled Minim with five minim or wearing tzitzit with more than 8 strings is an issue of Bal Tosif.
   2. For example, sprinkling a korban's blood more times than necessary can be a violation of Bal Tosif.
3. Some say that there's no prohibition of Baal Tosif to repeat a mitzvah several times. Some disagree.
   1. Some say that saying Shema at night before its time with intent to fulfill the mitzvah is Baal Tosif while others argue that there can't be Baal Tosif to say Shema since it is learning Torah.
   2. The Sephardic minhag to say Sefirat Haomer in the morning besides the night is an example of this.
   3. Saying Kedusha multiple times a day isn't Baal Tosif.
4. There is no issue of Baal Tosif when one's intention is to follow the Rabbis such as by keeping a second day of Yom Tov.
5. If it isn't the time of the mitzvah there's no way to violate Baal Tosif unless one has intention to fulfill the mitzvah then. For example, sleeping or eating in the Sukkah before Sukkot isn't an issue of Baal Tosif if one doesn't have intention to fulfill the mitzvah. After Sukkot is considered the time of the mitzvah and is a problem to sit in the Sukkah immediately after Sukkot even without intention.