When the time of prayer comes, call the Adhan, then call the iqamah, then the one who is oldest of you should act as your imam. The version narrated by Maslamah goes : He said: On that day we were almost equal in knowledge. The version narrated by Isma’il says: Khalid said: I said to Abu Qilabah: where is the Qur’an(i.e. why did the Prophet ﷺ not say: The one who knows the Qur’an most should act as imam)? He replied: Both of them were equal in the knowledge of the Qur’an.  

أَنَّ النَّبِيَّ ﷺ قَالَ لَهُ أَوْ لِصَاحِبٍ لَهُ إِذَا حَضَرَتِ الصَّلاَةُ فَأَذِّنَا ثُمَّ أَقِيمَا ثُمَّ لْيَؤُمَّكُمَا أَكْبَرُكُمَا وَفِي حَدِيثِ مَسْلَمَةَ قَالَ وَكُنَّا يَوْمَئِذٍ مُتَقَارِبَيْنِ فِي الْعِلْمِ وَقَالَ فِي حَدِيثِ إِسْمَاعِيلَ قَالَ خَالِدٌ قُلْتُ لأَبِي قِلاَبَةَ فَأَيْنَ الْقُرْآنُ قَالَ إِنَّهُمَا كَانَا مُتَقَارِبَيْنِ  

[Machine] "The Prophet ﷺ said to him and to his companion: 'When the prayer is due, both of you give the Adhan and establish it.' He said once, 'Then establish it, then let the one with the most knowledge among you lead the prayer.' Khalid said, 'So I asked Abu Qilaba, 'Where is the recitation?' He said, 'Indeed, they used to recite in a similar manner.'"  

أَنَّ النَّبِيَّ ﷺ قَالَ لَهُ وَلِصَاحِبٍ لَهُ إِذَا حَضَرَتِ الصَّلَاةُ فَأَذِّنَا وَأَقِيمَا وَقَالَ مَرَّةً فَأَقِيمَا ثُمَّ لِيَؤُمَّكُمَا أَكْبَرُكُمَا قَالَ خَالِدٌ فَقُلْتُ لِأَبِي قِلَابَةَ فَأَيْنَ الْقِرَاءَةُ؟ قَالَ إِنَّهُمَا كَانَا مُتَقَارِبَيْنِ  

[Machine] The Prophet ﷺ said to him and his companion, "When the prayer is due, give the call to prayer and then establish the prayer, and let the one with the loudest voice lead you." So I said to Abu Qilabah, "Where is the recitation?" He said, "They used to have similar recitations."  

أَنَّ النَّبِيَّ ﷺ قَالَ لَهُ وَلِصَاحِبٍ لَهُ «إِذَا حَضَرَتِ الصَّلَاةُ فَأَذِّنَا ثُمَّ أَقِيمَا وَلْيَؤُمَّكُمَا أَكْبَرُكُمَا» فَقُلْتُ لِأَبِي قِلَابَةَ فَأَيْنَ الْقِرَاءَةُ؟ فَقَالَ إِنَّهُمَا كَانَا مُتَقَارِبَيْنِ