Jamiat Tirmidhi

"I traveled with the Prophet, Abu Bakr, Umar, and Uthman; they would pray Zuhr and Asr as two Rak'ah and two Rak'ah, not praying before them nor after them." And Ibn Umar said: "If I was going to pray before it or after it then I would pray it complete."

"Imran bin Husain was asked about the traveler's prayer. He said: 'I performed Hajj with the Messenger of Allah, and he prayed two Rak'ah. I performed Hajj with Abu Bakr, and he prayed two Rak'ah and with Umar, and he prayed two Rak;ah; and with Uthman for six years of his Khilafah, or eight years, and he prayed two Rak'ah."

"We prayed Zuhr as four with the Prophet in Al-Madinah, and Asr as two Rak'ah in Dhil-Hulaifah."

"The Prophet went from Al-Madinah to Makkah, not fearing anyone except Allah the Lord of the worlds, and he prayed two Rak'ah."

that Anas bin Malik said: "We went with the Messenger of Allah from Al-Madinah to Makkah, and he prayed two Rak'ah." He said: "I said to Anas: 'How long did Messenger of Allah stay in Makkah?' He said: 'Ten (days).'"

"The Messenger of Allah traveled on a journey and he prayed two Rak'ah for nineteen days." Ibn Abbas said: "So when we would stay somewhere for nineteen (days) we would pray two Rak'ah , and if we stayed longer than that we would complete the Salat."

"I accompanied the Messenger of Allah on eighteen journeys, and I did not see him leave the two Rak'ah when the sun waned before Zuhr."