"… The best of speech is the Book of Allaah and the best of guidance is the guidance of Muhammad. The worst of things are those which are newly-invented, and every innovation is a going astray…" (Muslim)

There are some types of Bid'ah (innovations in religion) that we see so commonly that we almost grow to think it's part of Islam. Some of us actually have gone that far, and that's why they partake in these Bid'ahs to begin with. However, we do not realize the evil of innovating in the perfect religion of Allah. To innovate in it is to make some very serious and quite offensive allegations against either Allah or His Messenger, Sal-Allahu Alayhi wa Sallam, or both, and that is not something you want on your record.

To innovate in Islam is to present something to it which was not taught by the Messenger of Allah, Sal-Allahu Alayhi wa Sallam. Therefore, if we say that we can use this innovation, such as newly invented so-called "Islamic" holidays, or new types of worship, or anything attributed as being part of Islam which was not taught by the Prophet, Sal-Allahu Alayhi wa Sallam, then we are saying that this very same Prophet did not do a good job of teaching us our religion. We are thereby saying that either he did not know about this form of worship, and therefore was not able to teach it, or we are saying that he knew about it, but prevented us from benefiting from that knowledge.

If someone claims to know more about worshiping Allah than His Messenger, Sal-Allahu Alayhi wa Sallam, who Allah Himself guided to the peak of guidance and enveloped him in the greatest depth of humanly knowledge, even showing him Paradise and Hellfire during his lifetime, then such a person who claims this should re-assess if they are even a Muslim. Not only that, but they should realize that they are either accusing Allah of choosing someone incapable of correctly performing the job of being a messenger, or of not teaching us our religion and leaving us wandering around in misguidance until someone came along and "figured out" that this "new way of worship" will actually help us get into Jannah. We seek refuge with Allah from such evil and ignorance.

Likewise, if someone says that he, Sal-Allahu Alayhi wa Sallam, did know about this form of worship, but just did not teach it, then such a person is saying that the Messenger, Sal-Allahu Alayhi wa Sallam, was either unmindful when it came to delivering the message, or was forgetful and incapable, or that he did not know the value of it, and therefore did not see it necessary to deliver this piece of knowledge, or even that the Messenger Sal-Allahu Alayhi wa Sallam deceived us to "throw us off" so that we would not have the right tools to get into Jannah, Wal 'iyathu Billah.

These are the evil implications of introducing a new matter into the religion of Allah. Whoever does so it saying that something was either missing or something went wrong somewhere along the lines, until someone just "figured out" this new way of worship. Just as it is Haram to make any such claims, or even to imply a belief in the above claims, it is likewise Haram to innovate in Islam. Period. For Islam is perfect, and to add or subtract from perfection is falsehood in and of itself, and can only lead to inferiority:

And if you say that your deed is not a Bid'ah, and that what you're doing was, in fact, taught by Allah's Messenger, Sal-Allahu Alayhi wa Sallam, then bring your proof if you are truthful, for the burden of proof lies on the one who claims something exists, not on the one who claims it doesn't.