"I came to the Prophet ﷺ with a cousin of mine" - on an another occasion he said: "with a companion of mine" - "and he said: 'When the two of you travel, call the Adhan and the Iqamah, and let the older of you lead the prayer.'" (Using translation from Nasāʾī 634)
وَقَالَ مَرَّةً أَنَا وَصَاحِبٌ لِي النَّبِيَّ ﷺ فَقَالَ «إِذَا سَافَرْتُمَا فَأَذِّنَا وَأَقِيمَا وَلْيَؤُمَّكُمَا أَكْبَرُكُمَا»