Is it permissible to recite only a portion of a Surah during a rak'ah?

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It is permissible to recite only a portion of a Surah during a rak'ah. This is supported by the preceding hadiths which imply this allowance. Ahmad explicitly stated this position, citing the narration where Ibn Abza prayed behind 'Umar, who recited Surah Yusuf until reaching the verse "and his eyes turned white from grief" (Quran 12:84), at which point 'Umar began to weep, bowed, recited Surah An-Najm and prostrated, then stood up and recited Surah Az-Zalzalah. The permissibility is established because if limiting recitation to a single verse is allowed, then reciting a portion of the Surah is also permitted.