The Prophet ﷺ was on a journey, and when he stopped to rest, one of his companions came and walked beside him. The Prophet ﷺ turned to him and said, "Shall I tell you the best portion of the Quran?" Then he recited to him "All praise is due to Allah, Lord of all the worlds" [Fatihah 1:2].
كان النبي ﷺ في مسير فنزل فمشى رجل من أصحابه إلى جانبه، فالتفت إليه فقال: ألا أخبرك بأفضل القرآن؟ قال: فتلا عليه {الحمد لله رب العالمين}
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Nasai narrated it in Al-Yawm wal-Laylah (723), and Ibn Hibban graded it sahih (774), as did Hakim (1/560), all of them from the hadith of Ali bin Abdul-Hameed Al-Manee, who said, Sulayman bin Mughira narrated to us, from Thabit Bunani, from Anas bin Malik, who related it. Hakim said, "Sahih according to the criterion of Muslim."