Narrated Abu Hurairah:

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.

حَدَّثَنَا أَحْمَدُ بْنُ سَعِيدٍ الْهَمْدَانِيُّ، حَدَّثَنَا عَبْدُ اللَّهِ بْنُ وَهْبٍ، أَخْبَرَنِي مُسْلِمُ بْنُ خَالِدٍ، عَنِ الْعَلاَءِ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ 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 " . قَالَ أَبُو دَاوُدَ لَيْسَ هَذَا الْحَدِيثُ بِالْقَوِيِّ مُسْلِمُ بْنُ خَالِدٍ ضَعِيفٌ .