The theoretical dispute over bid'ah's scope, set out elsewhere in this collection, plays out concretely around a recurring set of contested practices, and looking at how scholars have actually ruled on them shows the abstract argument doing real work.
The Mawlid, the commemoration of the Prophet's birth, is the most widely contested case: celebrated with public gatherings and recitation across much of the Muslim world, it is defended by many Sunni scholars, including figures in the Ottoman and Sufi-oriented traditions, as an expression of love for the Prophet that falls under praiseworthy innovation, while Salafi and many Hanbali-oriented scholars reject it as an introduced festival with no basis in the practice of the earliest generations.
Congregational dhikr, the collective, sometimes rhythmic remembrance of God practiced in many Sufi orders, draws a similar division: defenders point to general Qur'anic and hadith encouragement to remember God frequently, while critics argue that the specific communal forms, particular postures, group vocalization, movement, were never practiced by the Prophet or his companions and therefore constitute an unwarranted addition to worship.
More recent technology has generated its own, lower-stakes version of the argument: the use of loudspeakers for the call to prayer was debated by twentieth-century scholars uncertain whether amplification changed the religious character of worship, a dispute largely resolved in favor of permission on the reasoning that the technology is a permissible means to an already-commanded end rather than an innovation in the substance of worship itself.