Of course there is a difference between sin and bid'ah. Sinner realizes that it is sin and embarrassed but he do sin. He knows he will be without goodness and will be punished. But the heretic thinks himself on the right path. He accuses others of not following him. He is sure that he will receive rewards for his bid'ah. Every person should be also away from bid'ah like other negative things.
1. The bid'ah in the aqidah is haram and can lead to disbelief if it contradicts explicitly against belief in religion.
If the bid'ah in the aqidah is inferior to what is mentioned above, and if it contradicts the aqeedah of ahl as-sunnah wal-jamaah sect, then it is a fisq.
2. The bid'ah in worship may be sometimes haram or sometimes makruh.
Examples of haram bid'ah are: fasting in the sun, and castrating himself to avoid approaching women.
An example of makruh bid'ah in worship is the mention of the Sultans in the Friday sermon and the excessively decorating of mosques.
The bid'ah in habits can be makruh or mubah: waste in eating and drinking is makruh, and impulsion of pleasure is mubah.
The causes of bid'ah:
1. Not knowing the teachings of the Quran and Sunnah.
2. Not understanding that the Shari'ah is flawless and perfect.
3. Not understanding that there are no contradictions in the verses of the Quran and hadiths.
4. Not knowing the origin of the Sunnah and its authenticity.
5. Excessive reliance on the mind.
6. Follow texts that mutashabih, are similar and difficult to understand by ordinary people.
7. Following the desires of the nafs
8. Keeping traditions tight.
9. Deeming what the ancestors did, as a religion.
10. Sticking to some critics' secs.
11. Following a defective mysticism.
12. Follow the dream.
The dangers of bid'ah:
1. Actions fail.
2. Satan will be close to the heretic.
3. The mixing of truth with falsehood.
4. The incitement of disrelish of those who do not know Islam.