It was narrated from Ibn Makhramah that:

Umar bin Al-Khattab, may Allah be pleased with him, said: "I heard Hisham bin Hakim bin Hizam reciting: Surat Al-Furqan, in a way that the Prophet of Allah ﷺ had not taught me. I said: 'Who taught you this Surah?' He said: 'The Messenger of Allah ﷺ.' I said: 'You are lying; the Messenger of Allah ﷺ did not teach you like that. 'I took him by the hand and brought him to the Messenger of Allah ﷺ and said: 'O Messenger of Allah, you taught me Surat Al-Furqan, but I heard this man reciting it in a way that you did not teach me.' The Messenger of Allah ﷺ said: 'Recite, O Hisham.' So he recited it as he had recited it (before). The Messenger of Allah ﷺ said: 'It was revealed like this.' Then he said: 'Recite, O Umar.' So I recited it, and he said: 'It was revealed like this.' Then the Messenger of Allah ﷺ said: 'The Quran was revealed to be recited in seven different modes.'"

أَخْبَرَنَا نَصْرُ بْنُ عَلِيٍّ، قَالَ أَنْبَأَنَا عَبْدُ الأَعْلَى، قَالَ حَدَّثَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، عَنْ عُرْوَةَ، عَنِ ابْنِ مَخْرَمَةَ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ، - رضى الله عنه - قَالَ سَمِعْتُ هِشَامَ بْنَ حَكِيمِ بْنِ حِزَامٍ، يَقْرَأُ سُورَةَ الْفُرْقَانِ فَقَرَأَ فِيهَا حُرُوفًا لَمْ يَكُنْ نَبِيُّ اللَّهِ ﷺ أَقْرَأَنِيهَا قُلْتُ مَنْ أَقْرَأَكَ هَذِهِ السُّورَةَ قَالَ رَسُولُ اللَّهِ ﷺ . قُلْتُ كَذَبْتَ مَا هَكَذَا أَقْرَأَكَ رَسُولُ اللَّهِ ﷺ فَأَخَذْتُ بِيَدِهِ أَقُودُهُ إِلَى رَسُولِ اللَّهِ ﷺ فَقُلْتُ يَا رَسُولَ اللَّهِ إِنَّكَ أَقْرَأْتَنِي سُورَةَ الْفُرْقَانِ وَإِنِّي سَمِعْتُ هَذَا يَقْرَأُ فِيهَا حُرُوفًا لَمْ تَكُنْ أَقْرَأْتَنِيهَا . فَقَالَ رَسُولُ اللَّهِ ﷺ " اقْرَأْ يَا هِشَامُ " . فَقَرَأَ كَمَا كَانَ يَقْرَأُ فَقَالَ رَسُولُ اللَّهِ ﷺ " هَكَذَا أُنْزِلَتْ " . ثُمَّ قَالَ " اقْرَأْ يَا عُمَرُ " . فَقَرَأْتُ فَقَالَ " هَكَذَا أُنْزِلَتْ " . ثُمَّ قَالَ رَسُولُ اللَّهِ ﷺ " إِنَّ الْقُرْآنَ أُنْزِلَ عَلَى سَبْعَةِ أَحْرُفٍ " .