ذِكْرُ خَبَرٍ ثَانٍ يُصَرِّحُ بِصِحَّةِ مَا ذَكَرْنَاهُ
Messenger of Allah ﷺ used to pray eleven rakʿat at night and that was his night prayer and each of his prostrations lasted for a period enough for one of you to recite fifty verses before Messenger of Allah ﷺ raised his head. He also used to pray two rakʿat (Sunnah) before the (compulsory) Fajr prayer and then lie down on his right side till the Mu'adh-dhin came to him for the prayer. (Using translation from Bukhārī 994)
«أَنَّ رَسُولَ اللَّهِ ﷺ كَانَ يُصَلِّي إِحْدَى عَشْرَةَ رَكْعَةً بِاللَّيْلِ فَكَانَتْ تِلْكَ صَلَاتُهُ يَسْجُدُ السَّجْدَةَ مِنْ ذَلِكَ بِقَدْرِ مَا يَقْرَأُ أَحَدُكُمْ خَمْسِينَ آيَةً قَبْلَ أَنْ يَرْفَعَ رَأْسَهُ وَيَرْكَعُ رَكْعَتَيْنِ قَبْلَ صَلَاةِ الْفَجْرِ ثُمَّ يَضْطَجِعُ عَلَى شِقِّهِ الْأَيْمَنِ حَتَّى يَأْتِيَهُ الْمُؤَذِّنُ لِلصَّلَاةِ»