What Do Invented Acts of Worship Lead To?

Indeed, al-bidaʿ¹ does not stop taking a person out of [the range of] minor sins to [that of] major [sins], until it finally takes him out into al-ilḥād² and al-zandaqah.³

¹acts of worship invented by people, not legislated by Allāh (tr.)
²opposing Islam as a non-Muslim (tr.)
³major hypocrisy: pretending to be a Muslim while hiding disbelief in Islam (tr.)

Majmūʿ Al-Fatāwá, vol. 22, p. 306.