It was narrated from ‘Isa bin Hafs bin ‘Asim bin ‘Umar bin Khattab that his father told him:
“We were with Ibn ‘Umar on a journey, and he led us in prayer. Then we finished with him and he finished turning around, and saw some people praying. He said: ‘What are these people doing?’ I said: ‘Glorifying Allah.’* He said: ‘If I wanted to glorify Allah (perform voluntary prayer) I would have completed my prayer. O son of my brother! I accompanied the Messenger of Allah (ﷺ) and he never prayed more than two Rak’ah when he was traveling, until Allah took his soul. Then I accompanied Abu Bakr and he never prayed more than two Rak’ah (when he was traveling), until Allah took his soul. Then I accompanied ‘Umar and he never prayed more than two Rak’ah, until Allah took his soul. Then I accompanied ‘Uthman and he never prayed more than two Rak’ah, until Allah took his soul. Allah says: ‘Indeed in the Messenger of Allah (Muhammad (ﷺ)) you have a good example to follow.’” [33:21]

Usamah bin Zaid said:
“I asked Tawus about performing voluntary prayer while traveling. Al-Hasan bin Muslim bin Yannaq was sitting with him and he said: ‘Tawus told me that he heard Ibn ‘Abbas say: “The Messenger of Allah (ﷺ) enjoined prayer while a resident and prayer when one is traveling. We used to pray when we were residents both before and after (the obligatory prayer), and we used to pray both before and after (the obligatory prayer) when we were traveling.’”