Is the act of remaining still (Tuma'ninah) in the bowing position (Ruku') obligatory during prayer?

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Remaining still (Tuma'ninah) in the bowing position, meaning lingering briefly after reaching the full bowing posture, is obligatory. This view is held by Al-Shafi'i. The evidence for this obligation is the command given by the Prophet, peace be upon him, to the one who prayed improperly, saying, 'Then bow until you are tranquil while bowing' (Muttafaqun 'alayh). Furthermore, it is related by Abu Qatadah that the Prophet, peace be upon him, stated that the worst thief is the one who steals from his prayer, explaining this as not perfecting the bowing or prostration. He also stated that prayer is not valid if a person does not straighten his back in the bowing and prostration. The divine command to bow is interpreted by the Prophet's action and speech; therefore, 'bowing' refers to what the Prophet clarified.