"He used to pray 'Isha, then he would recite tasbih, then after that he would pray whatever Allah (SWT) willed (he should pray) of night prayer. Then he would go and sleep for as long as he had prayed. Then he would get up from sleep and pray for as long as he had slept, and this last prayer of his would continue until dawn."
عَنْ صَلاَةِ رَسُولِ اللَّهِ ﷺ فَقَالَتْ كَانَ يُصَلِّي الْعَتَمَةَ ثُمَّ يُسَبِّحُ ثُمَّ يُصَلِّي بَعْدَهَا مَا شَاءَ اللَّهُ مِنَ اللَّيْلِ ثُمَّ يَنْصَرِفُ فَيَرْقُدُ مِثْلَ مَا صَلَّى ثُمَّ يَسْتَيْقِظُ مِنْ نَوْمِهِ ذَلِكَ فَيُصَلِّي مِثْلَ مَا نَامَ وَصَلاَتُهُ تِلْكَ الآخِرَةُ تَكُونُ إِلَى الصُّبْحِ