Selecting a surah is distinct from treating it as exclusively required. Frequent recitation for ease or memorization does not itself establish that one believes only this surah is lawful. The concern is turning a personal practice into a presumed obligation.
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Choosing a Surah Versus Exclusive Regularity
Prayer Recitation: Surah Selection, Minimum Amount and Following the Imam
Selecting a surah is distinct from treating it as exclusively required. Frequent recitation for ease or memorization does not itself establish that one believes only this surah is lawful. The concern is turning a personal practice into a presumed obligation.