‘Umar ibn al-Khattāb (may Allah be pleased with him) reported: I heard Hishām ibn Hakīm recite Sūrat al-Furqān during the lifetime of the Messenger of Allah (may Allah's peace and blessings be upon him). I listened to his recitation and noticed that he recited it in many ways which the Messenger of Allah (may Allah's peace and blessings be upon him) had not taught me. So I was about to jump upon him during the prayer, but I waited till he finished the prayer, whereupon I seized him by either his upper garment or mine and asked him: "Who taught you how to recite this Sūrah?" He replied: "The Messenger of Allah (may Allah's peace and blessings be upon him) taught me how to recite it." So I said to him: "You have told a lie! By Allah, the Messenger of Allah (may Allah's peace and blessings be upon him) taught me this Sūrah which I have heard you recite." So I set forth, leading him to the Messenger of Allah (may Allah's peace and blessings be upon him). I said: "O the Messenger of Allah, I heard this man recite Sūrat al-Furqān in ways which you have not taught me, and you taught me how to recite it." On that, the Messenger of Allah (may Allah's peace and blessings be upon him) said: "O ‘Umar, let go of him! Recite, O Hishām." So Hishām recited before him in the way I had heard him recite. the Messenger of Allah (may Allah's peace and blessings be upon him) said: "It was revealed like this." Then the Messenger of Allah (may Allah's peace and blessings be upon him) said: "Recite, O ‘Umar!" So I recited it. The Prophet (may Allah's peace and blessings be upon him) said: "It was revealed like this." And then he added: "Indeed, this Qur’an has been revealed in seven different ways, so recite it in the way that is easy for you."
Authentic hadith -
Narrated by Bukhari & Muslim