عَنْ قَيْسِ بْنِ عَمْرٍ رَضِيَ اللَّهُ عَنْهُ أَنَّهُ خَرَجَ إِلَى الصُّبْحِ فَوَجَدَ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ فِي الصُّبْحِ وَلَمْ يَكُنْ رَكَعَ رَكْعَتَي الْفَجْرِ فَصَلَّى مَعَ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ، ثُمَّ قَامَ حِينَ فَرَغَ مِنَ الصُّبْحِ فَرَكَعَ رَكْعَتَي الْفَجْرِ فَمَرَّ بِهِ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ فَقَالَ: ((مَا هَٰذِهِ الصَّلَاةُ؟)) فَأَخْبَرَهُ، فَسَكَتَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ وَلَمْ يَقُلْ شَيْئًا
It is narrated from Sayyiduna Qais bin Amr (may Allah be pleased with him) that he came for the Fajr prayer and found the Noble Prophet (peace and blessings be upon him) in the Fajr prayer, while he had not performed the two Sunnah of Fajr. So he prayed with the Prophet (peace and blessings be upon him), and when the Fajr prayer was finished, he stood up to perform the Sunnah of Fajr. When the Prophet (peace and blessings be upon him) passed by him, he asked: "Which prayer is this?" He informed the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) remained silent and did not say anything.