"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."
Jami` at-Tirmidhi Book 6, Hadith 6
← Previous Hadith 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).'"

Jami` at-Tirmidhi Book 6, Hadith 5 Next Hadith → "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."

Jami` at-Tirmidhi Book 6, Hadith 7