Imam Ali (AS) said, ‘When sleep overcomes you while you are in your prayer, then break your prayer and go to sleep, for verily [in that state] you do not know if you are praying for or against yourself!
الإمامُ عليٌّ (عَلَيهِ الّسَلامُ): إذا غَلَبَتكَ عَينُكَ وأنتَ في الصَّلاةِ فاقطَعِ الصَّلاةَ ونَم؛ فإنَّكَ لا تَدرِي تَدعُو لك أو على نفسِكَ!
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Man Lā Yaḥḍuruh al-Faqīh #1376"If a man is overcome by sleep while he is in prayer, let him put his head down and sleep, for I fear that if he wishes to say, 'O’ Allah...