"And the one that did not die in its sleep," meaning: and He takes the soul of the one that did not die; that is, He takes it during its sleep. "Then He keeps that for which He has decreed death," meaning: then He causes it to die.
Muhammad said: "Fayumsiku" (Then He keeps) in the nominative case is the recitation of Nafi'.
"And sends the other back until a specified term," until death. That is because when a human sleeps, the nafs (soul/self) departs while the ruh (spirit) remains, and there is between them something like the rays of the sun. And it has reached us that
﴿وَالَّتِي لَمْ تَمُتْ فِي مَنَامِهَا﴾ أَي ويتوفى الَّتِي لمْ تمت؛ أَي: يتوفاها فِي منامها ﴿فَيُمْسِكُ الَّتِي قضى عَلَيْهَا الْمَوْت﴾ أَي: فيميتها.
قَالَ محمدٌ: (فَيُمْسِكُ) بِالرَّفْع هِيَ قِرَاءَة نَافِع.
﴿وَيُرْسِلُ الْأُخْرَى إِلَى أجل مُسَمّى﴾ إِلَى الْمَوْت؛ وَذَلِكَ أَن الْإِنْسَان إِذا نَام خرجت النَّفس وَتبقى الرّوح فَيكون بَينهمَا مثل شُعَاع الشَّمْس , وبلغنا أَن
