Abu Hurairah reported,
The Messenger of Allah ﷺ said, "The Quran was revealed in seven modes. Disputing about the Quran is disbelief," repeating it three times. "Whatever you understand of it, act upon, and whatever you do not understand of it, refer back to one who knows."
Azami 11762
Sahihعن أبي هريرة قال
إن رسول الله ﷺ قال: نزل القرآن على سبعة أحرف، المراء في القرآن كفر- ثلاث مرات- فما عرفتهم منه فاعملوا، وما جهلتم منه فردوه إلى عالمه.
Ahmad (7989) narrated it from Anas bin Iyad, who said, Abu Hazim told me, from Abu Salama, who said, "I do not know it except from Abu Hurairah," and then related it.Nasai narrated it in Fadail al-Quran (118), and Ibn Hibban in his Sahih (74), by this same route, without the doubt.Ahmad (8390) also narrated it through another route, from Abu Salama, from Abu Hurairah, who said, the Messenger of Allah ﷺ said, "Allah 
sent down the Quran in seven letters, All-Knowing, All-Wise, Oft-Forgiving, Merciful."