Prayer (Kitab Al-Salat): Detailed Rules of Law about the Prayer during Journey

Dawud :: Book 4 : Hadith 1225

Narrated Imran ibn Husayn:

I went on an expedition with the Apostle of Allah (peace_be_upon_him), and I was present with him at the conquest. He stayed eighteen days in Mecca and prayed only two rak'ahs (at each time of prayer). And he said: You who live in the town must pray four; we are travellers.