Is prayer obligatory to be repeated if some of its pillars - such as devotion - were missed due to the imam's speed?

If the Imam's speed in prayer does not compromise tranquility (ṭumaʾnīnah), then the prayer is valid. The definition of tranquility is the settling of the limbs in the posture of the pillar (rukn). However, if his speed compromises tranquility, then the prayer is invalid and must be repeated by both the Imam and the congregant. The loss of devotion (khushūʿ) due to the Imam's speed does not invalidate the prayer.