The Prophet ﷺ used to recite in the dawn prayer "Qaf. By the glorious Quran" [Qaf 50:1], and his prayer afterward became lighter.
إن النبي ﷺ كان يقرأ في الفجر: ب {ق والقرءان المجيد} وكانت صلاته بعد تخفيفا.
Muslim narrated it in the Book of Prayer (458) through Zaida, from Simak, from Jabir, who related the hadith.Zuhayr also narrated it from Simak, who said, I asked Jabir bin Samura about the prayer of the Messenger of Allah ﷺ, and he said, "He used to shorten the prayer, and he did not pray the way these people do."Shubah also narrated it from Simak, and in his version it says, The Prophet ﷺ used to recite in Dhuhr "By the night when it covers" [Layl 92:1], and something similar in Asr, and in Fajr something longer than that.In another version, He used to recite in Dhuhr "Glorify the name of your Lord, the Most High" [Ala 87:1], and in Fajr something longer than that.