The Messenger of Allah ﷺ came out and saw that the people were praying during (the night of) Ramadan in the corner of the mosque. He asked: Who are these people ? It was said to him that those were people who had not learnt Quran. But Ubayy b. Ka'b is praying and they would pray behind him. The Prophet ﷺ said: They did right and it is good what they did. Abu Dawud said: This tradition is not strong, the narrator Muslim b. Khalid is weak.
خَرَجَ رَسُولُ اللَّهِ ﷺ فَإِذَا أُنَاسٌ فِي رَمَضَانَ يُصَلُّونَ فِي نَاحِيَةِ الْمَسْجِدِ فَقَالَ مَا هَؤُلاَءِ فَقِيلَ هَؤُلاَءِ نَاسٌ لَيْسَ مَعَهُمْ قُرْآنٌ وَأُبَىُّ بْنُ كَعْبٍ يُصَلِّي وَهُمْ يُصَلُّونَ بِصَلاَتِهِ فَقَالَ النَّبِيُّ ﷺ أَصَابُوا وَنِعْمَ مَا صَنَعُوا