Umar bin Khattab reported,

I heard Hisham bin Hakeem reciting Surah al-Furqan during the lifetime of the Messenger of Allah ﷺ. I listened carefully to his recitation, and found him reciting it according to many readings that the Messenger of Allah ﷺ had not taught me. I nearly accosted him in the middle of his prayer, but I restrained myself until he finished. Then I seized him by his cloak and said, "Who taught you this surah I just heard you reciting?"He replied, "The Messenger of Allah ﷺ taught it to me."I said, "You are lying. The Messenger of Allah ﷺ taught it to me differently than what you recited."So I led him along to the Messenger of Allah ﷺ and said, "I heard this man reciting Surah al-Furqan according to readings you did not teach me."He said, "Let him go. Recite, Hisham."So Hisham recited it the way I had heard him recite it, and the Messenger of Allah ﷺ said, "Thus it was revealed."Then the Messenger of Allah ﷺ said, "Recite, Umar."So I recited it the way he had taught me, and he said, "Thus it was revealed. This Quran was revealed in seven readings, so recite whichever of them is easy for you."

Bukhari 7550

Sahih

حدثنا يحيى بن بكير حدثنا الليث عن عقيل عن ابن شهاب حدثني عروة أن المسور بن مخرمة وعبد الرحمن بن عبد القاري حدثاه أنهما سمعا

عمر بن الخطاب يقول

سمعت هشام بن حكيم يقرأ سورة الفرقان في حياة رسول الله ﷺ فاستمعت لقراءته فإذا هو يقرأ على حروف كثيرة لم يقرئنيها رسول الله ﷺ فكدت أساوره في الصلاة فتصبرت حتى سلم فلببته بردائه فقلت من أقرأك هذه السورة التي سمعتك تقرأ قال أقرأنيها رسول الله ﷺ فقلت كذبت أقرأنيها على غير ما قرأت فانطلقت به أقوده إلى رسول الله ﷺ فقلت إني سمعت هذا يقرأ سورة الفرقان على حروف لم تقرئنيها فقال أرسله اقرأ يا هشام فقرأ القراءة التي سمعته فقال رسول الله ﷺ كذلك أنزلت ثم قال رسول الله ﷺ اقرأ يا عمر فقرأت التي أقرأني فقال كذلك أنزلت إن هذا القرآن أنزل على سبعة أحرف فاقرءوا ما تيسر منه

البخاري 7550صحيح
Contents
Reference
Commentary
Ayat
Collection
Sahih Bukhari
Book
Tawhid
Chapter
His saying, "So recite what is easy from the Quran"
Numbering
Darussalam 7550
Bukhari 7550