He went out for the dawn prayer and found the Prophet ﷺ already praying it, having not yet prayed the two units of Fajr. So he prayed with the Prophet ﷺ, and when the dawn prayer was finished, he stood up and prayed the two units of Fajr.The Prophet ﷺ passed by him and asked, "What prayer is this?"He told him, and the Prophet ﷺ remained silent and went on without saying anything.
حدثنا عبد الرزاق أنبأنا ابن جريج قال
خرج إلى الصبح فوجد النبي ﷺ في الصبح ولم يكن ركع ركعتي الفجر فصلى مع النبي ﷺ ثم قام حين فرغ من الصبح فركع ركعتي الفجر فمر به النبي ﷺ فقال ما هذه الصلاة فأخبره فسكت النبي ﷺ ومضى ولم يقل شيئا
No references are available.
Its isnad is sahih, if Abd Rabbih's hearing from his grandfather is confirmed, but it is not confirmed. So it is disconnected. The hadith is like the one before it.