Sunan Abi Dawud 21049
In-book no 545حَدَّثَنَا عَبْدُ اللَّهِ بْنُ إِسْحَاقَ الْجَوْهَرِيُّ، أَخْبَرَنَا أَبُو عَاصِمٍ، عَنِ ابْنِ جُرَيْجٍ، عَنْ مُوسَى بْنِ عُقْبَةَ، عَنْ سَالِمٍ أَبِي النَّضْرِ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم حِينَ تُقَامُ الصَّلاَةُ فِي الْمَسْجِدِ إِذَا رَآهُمْ قَلِيلاً جَلَسَ لَمْ يُصَلِّ وَإِذَا رَآهُمْ جَمَاعَةً صَلَّى .
Abu al-Nadr said: when the Iqamah was pronounced and the Messenger of Allah (ﷺ) saw that they (the people) were small in number, he would sit down, nd would not pray; but when he saw them (the people) large in number, he would pray.