"The lightning almost snatches away their sight" [even as they manifested faith and concealed disbelief] due to its intense light. "Whenever it lights up for them, they walk therein, and when it becomes dark for them, they stand still," meaning: they remain unable to see. "And if Allah had willed, He could have taken away their hearing and their sight," at the time they manifested faith and concealed disbelief.
Muhammad said: His saying, "Or like a downpour from the sky," means: Or like the people of a downpour. The word "or" (aw) is used here not for doubt; it is of the type that grammarians say is used for permissibility (al-ibahah).
The meaning is: that the analogy (tamthil) is permissible for you regarding the hypocrites; if you liken them to the one who kindled a fire, then that is their likeness, and if you liken them to the people of the downpour, then that is their likeness. It is said: the rain 'saba' (descended) to 'yasubu' (descend); when it falls. [Verse 21-23]
﴿يكَاد الْبَرْق يخطف أَبْصَارهم﴾ [حَتَّى أظهرُوا الإِيمَان وأسروا الشّرك] لشدَّة ضوئه ﴿كُلَّمَا أَضَاءَ لَهُمْ مَشَوْا فِيهِ وَإِذَا أَظْلَمَ عَلَيْهِمْ قَامُوا﴾ أَي: بقوا لَا يبصرون ﴿وَلَوْ شَاءَ اللَّهُ لَذَهَبَ بِسَمْعِهِمْ وَأَبْصَارِهِمْ﴾ حِين أظهرُوا الإِيمَان، وأسروا الشّرك.
قَالَ مُحَمَّد: قَوْله: ﴿أَوْ كَصَيِّبٍ من السَّمَاء﴾ مَعْنَاهُ: أَو كأصحاب صيب، و ((أَو)) دخلت هَذَا لغير شكّ؛ وَهِي الَّتِي يَقُولُ النحويون: إِنَّهَا تدخل للْإِبَاحَة.
وَالْمعْنَى: أَن التَّمْثِيل مُبَاح لكم فِي الْمُنَافِقين؛ إِن مثلتموهم بِالَّذِي استوقد نَارا فَذَلِك مثلهم، وَإِن مثلتموهم بأصحاب الصيب فَهُوَ مثلهم. وَيُقَال: صاب الْمَطَر يصوب؛ إِذا نزل. [آيَة ٢١ - ٢٣]
