It was narrated that Ibn Buhainah said:

"The Iqamah for Subh prayer was said, and the Messenger of Allah ﷺ saw a man praying while the Mu'adhdhin saying the Iqamah. He said: 'Are you praying Subh with four
Rak'ahs?"'

أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ سَعْدِ بْنِ إِبْرَاهِيمَ، عَنْ حَفْصِ بْنِ عَاصِمٍ، عَنِ ابْنِ بُحَيْنَةَ، قَالَ أُقِيمَتْ صَلاَةُ الصُّبْحِ فَرَأَى رَسُولُ اللَّهِ ﷺ رَجُلاً يُصَلِّي وَالْمُؤَذِّنُ يُقِيمُ فَقَالَ " أَتُصَلِّي الصُّبْحَ أَرْبَعًا " .