"I came to the Messenger of Allah ﷺ with a cousin of mine" - once he said, "with a friend of mine" - and he said: 'When you travel, call the Adhan and Iqamah, and let the older of you lead the prayer.'"  

أَتَيْتُ رَسُولَ اللَّهِ ﷺ أَنَا وَابْنُ عَمٍّ لِي وَقَالَ مَرَّةً أَنَا وَصَاحِبٌ لِي فَقَالَ إِذَا سَافَرْتُمَا فَأَذِّنَا وَأَقِيمَا وَلْيَؤُمَّكُمَا أَكْبَرُكُمَا