The travelers’ prayer and shortening it

Hafs b. 'Asim said: I accompanied Ibn 'Umar on the road to Mecca and he led us in two rak'ahs at the noon prayer, then he went forward and we too went along with him to a place where he alighted, and he sat and we sat along with him, and he cast a glance to the side where he said prayer and he saw people standing and asked: What are they doing? I said: They are engaged in glorifying Allah, offering Sunnah prayer. He said: If I had done so I would have perfected my prayer; O my nephew! I accompanied the Messenger of Allah (ﷺ) on a journey, and he made no addittion to two rak'ahs, till Allah called him. I accompanied Abu Bakr and he made no addition to two rak'ahs till Allah caused him to die. I accompanied 'Umar and he made no addition to two rak'ahs till Allah caused him to die. I accompanied 'Uthman and he made no addition to two rak'ahs, till Allah caused him to die, and Allah has said:" There is a model pattern for you in the Messenger of Allah" (al-Qur'an, xxxiii. 21).