'Umar b. al-Khattab said:

I heard Hisham b. Hakim (b. Hizam) reciting Surah al-Furqan in a different manner from my way of reciting, and the Messenger of Allah ﷺ had taught me to recite it. I nearly spoke sharply to him, but I delayed till he had finished. Then I caught his cloak at the neck, and I brought him to the Messenger of Allah ﷺ. I said: Messenger of Allah, I heard this man reciting Surah al-Furqan in a manner different from that in which you taught me to recite it. The Messenger of Allah ﷺ the told him to recite it. He then recited in the manner I heard him recite. The Messenger of Allah ﷺ said: Thus was it sent down. He then said to me: Recite, I recited (it). He then said: Thus was it sent down. He said: The Qur'an was sent down in seven modes of reading, so recite according to what comes most easily.

حَدَّثَنَا الْقَعْنَبِيُّ، عَنْ مَالِكٍ، عَنِ ابْنِ شِهَابٍ، عَنْ عُرْوَةَ بْنِ الزُّبَيْرِ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ عَبْدٍ الْقَارِيِّ، قَالَ سَمِعْتُ عُمَرَ بْنَ الْخَطَّابِ، يَقُولُ سَمِعْتُ هِشَامَ بْنَ حَكِيمِ بْنِ حِزَامٍ، يَقْرَأُ سُورَةَ الْفُرْقَانِ عَلَى غَيْرِ مَا أَقْرَؤُهَا وَكَانَ رَسُولُ اللَّهِ ﷺ أَقْرَأَنِيهَا فَكِدْتُ أَنْ أَعْجَلَ عَلَيْهِ ثُمَّ أَمْهَلْتُهُ حَتَّى انْصَرَفَ ثُمَّ لَبَّبْتُهُ بِرِدَائِهِ فَجِئْتُ بِهِ رَسُولَ اللَّهِ ﷺ فَقُلْتُ يَا رَسُولَ اللَّهِ إِنِّي سَمِعْتُ هَذَا يَقْرَأُ سُورَةَ الْفُرْقَانِ عَلَى غَيْرِ مَا أَقْرَأْتَنِيهَا . فَقَالَ لَهُ رَسُولُ اللَّهِ ﷺ " اقْرَأْ " . فَقَرَأَ الْقِرَاءَةَ الَّتِي سَمِعْتُهُ يَقْرَأُ فَقَالَ رَسُولُ اللَّهِ ﷺ " هَكَذَا أُنْزِلَتْ " . ثُمَّ قَالَ لِي " اقْرَأْ " . فَقَرَأْتُ فَقَالَ " هَكَذَا أُنْزِلَتْ " . ثُمَّ قَالَ " إِنَّ هَذَا الْقُرْآنَ أُنْزِلَ عَلَى سَبْعَةِ أَحْرُفٍ فَاقْرَءُوا مَا تَيَسَّرَ مِنْهُ " .