وَعَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ ذَلِكَ قَدْ فَعَلَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَصَرَ الصَّلَاةَ وَأَتَمَّ. رَوَاهُ فِي شرح السّنة

‘Imran b. Husain said

I went on an expedition with the Prophet, and I was present with him at the Conquest. He stayed eighteen days in Mecca and prayed only two rak'as [at each time of prayer]. He said, “You who live in the town must pray four; we are travellers.” Abu Dawud transmitted it.