Shaykh Al Uthaymeen was asked
You mentioned that no innovation has been innovated except that similar to it from the Sunnah has been left off as one of the Salaf said. Thus what is the left off Sunnah due to innovating the innovation of Mawlid (the prophets birthday)?
The Sunnah left off, is leaving it, leaving off this innovation (Mawlid), because the Sunnah could be by way of leaving off something or by action. If the messenger of Allah صلى الله عليه و سلم left off something whilst the means for the action were present, and he didn’t do it, then leaving it off is Sunnah.
Thus here we say, you innovated an innovation and you left off a Sunnah, and the Sunnah here is leaving off the innovation!
Majid Jawed Al-Afghanee