Is tranquility obligatory throughout the entire prayer, and does doubt concerning its absence necessitate repeating the prayer?

Tranquility is obligatory in all pillars of prayer. The limit of tranquility while standing is to stand upright and recite Al-Fatiha. As for bowing (ruku'), prostration (sujud), and the two moderate standing positions (i'tidalain), its limit is to pause for a duration sufficient for the prescribed remembrance (dhikr). This duration is considered the attainment of tranquility. Tranquility is the sufficient time to achieve the pillar. In bowing and prostration, merely uttering the obligatory dhikr, such as "Subhana Rabbiyal-Azeem" (Glory be to my Lord, the Most Great) once, with stillness, counts as tranquility. Furthermore, tranquility is not negated by moving a hand or foot during prayer, because this is a slight movement that is excused and does not affect the validity of the prayer.