Is sitting in the final Tashahhud with the left foot tucked under and the right foot upright an act of Bidʻah (innovation)?

We have previously clarified the sayings of the jurists regarding the description of the sitting posture in the final Tashahhud, and we favored the view of the Hanbalis as being closer to the Sunnah. Thus, it is Sunnah for the worshiper to practice tawarruk in the final Tashahhud in prayers that have two Tashahhuds. In all other instances, the worshiper should practice iftirash, placing the right foot upright and sitting on the left foot.

According to the Shafi'is, the sitting posture is tawarruk in every final Tashahhud in prayer, whether the prayer is four rak'ahs or less. So, one performs tawarruk in every Tashahhud from which one gives the salam, even if it is not the second one, such as the Tashahhud of Fajr and Jumu'ah.

The description of tawarruk is that the worshiper places the right foot upright, positions the sole of the left foot under the right thigh, and places both buttocks on the ground. Alternatively, one extends both feet to the right side while they are in the iftirash posture, allowing the hip to rest on the ground.

If there are people of innovation who adopt this sitting posture, then this is something in which they have conformed to the Sunnah. This Sunnah should not be abandoned merely because people of innovation practice it.