(Indeed, shirk [polytheism] is a great injustice), meaning: the polytheist wrongs himself by it and diminishes it.
﴿إِن الشّرك لظلم عَظِيم﴾ يَعْنِي: يَظْلِمُ بِهِ الْمُشْرِكُ نَفْسَهُ وينقصها.
