The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1481
Ibn 'Umar reported: The Apostle of Allah (may peace be upon him) said in Mina the prayer of a traveller (short prayer) ; Abu Bakr and 'Umar did the same and 'Uthmia did it for eight years or six years. Hafs (one of the narrators) said: Ibn 'Umar would also say two rak'ahs at Mina and then go to bed. I said to him: O uncle, I wish you could have said two rak'ahs (of Sunnah prayer after shorenting the Fard prayer). He said: Were I to do that, I would have completed the prayer.