"Allah is the ally of those who believe." Al-Hasan said: He is the ally of their guidance and their success. "He brings them out of darknesses into the light," meaning: from misguidance into guidance. "And those who disbelieve—their allies are the Taghut (false deities/Satan). They bring them out of the light into darknesses," from guidance into misguidance.
Muhammad said: The term 'Taghut' here is singular but carries the meaning of a plural group; this is permissible in the language when there is an indication in the speech that refers to a group. [Verse 258]
﴿الله ولي الَّذين آمنُوا﴾ قَالَ الحَسَن: وَلِي هدَاهُم وتوفيقهم ﴿يُخْرِجُهُمْ مِنَ الظُّلُمَاتِ إِلَى النُّوُرِ﴾ يَعْنِي: من الضَّلَالَة إِلَى الْهدى ﴿وَالَّذِينَ كَفَرُوا أَوْلِيَاؤُهُمُ الطَّاغُوتُ يُخْرِجُونَهُمْ من النُّور إِلَى الظُّلُمَات﴾ من الْهدى إِلَى الضَّلَالَة.
قَالَ مُحَمَّد: والطاغوت هَا هُنَا وَاحِد فِي معنى جمَاعَة؛ وَهَذَا جَائِز فِي اللُّغَة؛ إِذا كَانَ فِي الْكَلَام دَلِيل عَلَى الْجَمَاعَة. [آيَة ٢٥٨]
