The Prophet ﷺ had a mat which he used to spread during the day and use as a curtain at night. So a number of people gathered at night facing it and prayed behind him.  

أَنَّ النَّبِيَّ ﷺ كَانَ لَهُ حَصِيرٌ يَبْسُطُهُ بِالنَّهَارِ وَيَحْتَجِرُهُ بِاللَّيْلِ فَثَابَ إِلَيْهِ نَاسٌ فَصَلَّوْا وَرَاءَهُ  

Messenger of Allah ﷺ made a small room in the month of Ramadan (Saʿid said, "I think that Zaid bin Thabit said that it was made of a mat") and he prayed there for a few nights, and so some of his companions prayed behind him. When he came to know about it, he kept on sitting. In the morning, he went out to them and said, "I have seen and understood what you did. You should pray in your houses, for the best prayer of a person is that which he prays in his house except the compulsory prayers."  

أَنَّ رَسُولَ اللَّهِ ﷺ اتَّخَذَ حُجْرَةً قَالَ حَسِبْتُ أَنَّهُ قَالَ مِنْ حَصِيرٍ فِي رَمَضَانَ فَصَلَّى فِيهَا لَيَالِيَ فَصَلَّى بِصَلاَتِهِ نَاسٌ مِنْ أَصْحَابِهِ فَلَمَّا عَلِمَ بِهِمْ جَعَلَ يَقْعُدُ فَخَرَجَ إِلَيْهِمْ فَقَالَ قَدْ عَرَفْتُ الَّذِي رَأَيْتُ مِنْ صَنِيعِكُمْ فَصَلُّوا أَيُّهَا النَّاسُ فِي بُيُوتِكُمْ فَإِنَّ أَفْضَلَ الصَّلاَةِ صَلاَةُ الْمَرْءِ فِي بَيْتِهِ إِلاَّ الْمَكْتُوبَةَ