1

This question already has an answer here:

According to Devarim 4:2 (and 13:1), there are to be no additions to the Torah ('Do not add to what I command you and do not subtract from it, but keep the commands of the Lord your God that I give you . . . All this word which I command you, that shall you observe to do; you shall not add thereto, nor diminish from it') In light of that, how are the feasts of Purim and Hanukkah, two additional feasts, justified? Even further, Shemini Azeret and Simchat Torah?

marked as duplicate by Joel K, msh210 May 27 at 13:09

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.