Is the confirmed Sunnah considered an obligatory duty (fard), and is one sinful for saying it is an obligatory duty?

The confirmed Sunnah (Sunnah Mu'akkadah) is that which the Prophet, peace and blessings be upon him, consistently practiced, and there is evidence indicating that it is not obligatory. Scholars' opinions on it vary; some consider it obligatory, while others view it as a recommended Sunnah. If the speaker, by "confirmed Sunnah is an obligation (fard)," meant the obligatory duties, then he is not mistaken, as "fard" (obligation) and "wajib" (duty) are synonymous according to the majority of scholars. However, if he meant other Sunnahs that are not considered obligatory by the general body of jurists, then he has erred and must repent, because it is not permissible to describe something as obligatory without evidence or reliance on the statements of the Imams.