It is narrated from Abdur Rahman bin Abd al-Qari (may Allah have mercy on him), he says: I heard Umar bin Khattab (may Allah be pleased with him) stating that once I heard Hisham bin Hakim bin Hizam (may Allah be pleased with him) reciting Surah Al-Furqan in a manner different from the way I recite it. Although the Messenger of Allah ﷺ himself had taught me that recitation. I was about to become angry with him, but then I gave him respite until he finished the prayer. When he finished, I wrapped his own cloak around his neck and dragged him to the Messenger of Allah ﷺ. I said, "I have heard him reciting in a way different from what you taught me." The Messenger of Allah ﷺ said to Hisham (may Allah be pleased with him), "Recite!" So he recited in the manner I had heard him recite. Then the Messenger of Allah ﷺ said, "It was revealed in this way." Then he said to me, "You recite!" So I recited, and he ﷺ said, "It was revealed in this way also. Indeed, the Qur'an was revealed in seven dialects, so recite in whichever is easy for you."
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 397
Hadith Takhrijاخرجہ البخاری، الخصومات، باب کلام الخصوم بعضہم فی بعض (2419) ومسلم، صلاۃ المسافرین، باب بیان ان القرآن انزل علی سبعۃ احرف، وبیان معناہا (818)۔