"Moses said: 'Is it magic, that which you have brought?'" Muhammad said: 'Ma' (that which) is in the sense of 'alladhi' (that which); meaning: that which you have brought is magic.
﴿قَالَ مُوسَى مَا جِئْتُمْ بِهِ السحر﴾ قَالَ محمدٌ: (مَا) بِمَعْنَى الَّذِي؛ أَيْ: الَّذِي جِئْتُمْ بِهِ السِّحْرُ.
