Allah's Messenger (ﷺ) said, "The Um (substance) of the Quran is the seven oft-repeated verses (Al- Mathaini) and is the Great Quran (i.e. Surat-al-Fatiha).
Sahih al-Bukhari Book 65, Hadith 226
← Previous Hadith While I was praying, the Prophet (ﷺ) passed by and called me, but I did not go to him till I had finished my prayer. When I went to him, he said, "What prevented you from coming?" I said, "I was praying." He said, "Didn't Allah say" "O you who believes Give your response to Allah (by obeying Him) and to His Apostle." (8.24) Then he added, "Shall I tell you the most superior Sura in the Quran before I go out of the mosque?" When the Prophet (ﷺ) intended to go out (of the Mosque), I reminded him and he said, "That is: "Al hamdu-li l-lahi Rabbil-`alamin (Surat-al-fatiha)' which is the seven oft repeated verses (Al-Mathani) and the Grand Quran which has been given to me."

Sahih al-Bukhari Book 65, Hadith 225 Next Hadith → Those who have made their Scripture into parts are the people of the Scripture who divided it into portions and believed in a part of it and disbelieved the other.

Sahih al-Bukhari Book 65, Hadith 227