Surah 6:108
"Do not revile those (gods) on whom they call instead of God, or they will revile God in enmity without any knowledge. In this way We make their deed(s) appear enticing to every community. Then to their Lord is their return, and He will inform them about what they have done."
6.108 – Do not revile those (gods) on whom they call instead of Allah
The Quran commands believers not to insult or abuse (sabba) the objects of people’s worship apart from Allah. This verb appears only here in the Quran, but in later Islamic history this became one of the main verbs used to allege “blasphemy” against Muhammad.
- from The Quran with Christian Commentary: A Guide to Understanding the Scripture of Islam