Do you know of any scholar who said that the ‘Asr prayer that is prayed after the shadow of an object becomes twice the height of the object (the time when Hanafis pray ‘Asr) will be completely invalid and unacceptable?

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We do not know of any scholar who held that the ‘Asr prayer performed when the shadow of an object becomes twice its height is invalid. Rather, some scholars maintained that the optional time of the ‘Asr ends at that time, not that the time of the prayer comes to an end. Other scholars held that a person bears a sin for delaying the ‘Asr prayer beyond that time and that it is considered Qadhaa' (making up for a missed prayer), but not that it is invalid or unacceptable.

An-Nawawi wrote, “The time of the ‘Asr prayer ends with sunset. This is the most likely correct view stated by Ash-Shaafi‘i and is held as the only sound view by the majority of his followers. Abu Sa‘eed Al-Istakhri held that the end of the time of the ‘Asr is when the shadow of an object becomes twice its height and that if the person delayed the prayer beyond this time, he bears a sin and it is considered Qadhaa'...” [Al-Majmoo’]

Allah knows best.