Abu Huraira reported: The Messenger of Allah (ﷺ) said: He who said his prayer, but did not recite the opening chapter of al-Kitab, his prayer is incomplete. He repeated it thrice
Book 4 · Hadith 43
صحيح مسلم
Abu Huraira reported: The Messenger of Allah (ﷺ) said: He who said his prayer, but did not recite the opening chapter of al-Kitab, his prayer is incomplete. He repeated it thrice