Sunan an-Nasa'i 782
It was narrated from Abu Sa'eed that the Prophet (ﷺ) said:
"when there are three people let one of them lead the prayer, and the one who is most entitled to lead the prayer is the one who has 
most knowledge of the Qur'an."
أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ سَعِيدٍ، عَنْ يَحْيَى، عَنْ هِشَامٍ، قَالَ حَدَّثَنَا قَتَادَةُ، عَنْ أَبِي نَضْرَةَ، عَنْ أَبِي سَعِيدٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏
"‏ إِذَا كَانُوا ثَلاَثَةً فَلْيَؤُمَّهُمْ أَحَدُهُمْ وَأَحَقُّهُمْ بِالإِمَامَةِ أَقْرَؤُهُمْ ‏"‏ ‏.‏