What the Oral Torah Says About This

Deuteronomy 4:2 and 13:1 

The Pharisees discussed the prohibitions against adding to or taking away from the laws of the Torah (Deuteronomy 4:2 and Deuteronomy 13:1). They called these prohibitions Bal Tosif and Bal Tigra. 

Maimonades Law of Rebellion 2:9  

Ecclesiastes Rabba 3:1 

B. Megillah 14a 

Rosh Hashanah 28b

These are pronouncements on the substantive law of Torah that have not followed the procedural laws of Torah. Torah procedural laws tell us that substantive laws can only be made by Priests, Levites and Judges.

Non-Affiliated source: Sefaria 'Bal Tosif Sources and Sheets'

Non-Affiliated Source: Rabbi Yuter 

Download the PDF by Rabbi Yuter

Visit the site of Rabbi Yuter for more materials on Bal Tosif/Bal Tigra