(5) باب يَقْصُرُ إِذَا خَرَجَ مِنْ مَوْضِعِهِ
Narrated `Aisha:
"When the prayers were first enjoined they were of two rak`at each. Later the prayer in a journey was kept as it was but the prayers for non-travelers were completed." Az-Zuhri said, "I asked `Urwa what made Aisha pray the full prayers (in journey)." He replied, "She did the same as `Uthman did."
Reference: Sahih al-Bukhari 1090
In-book reference: Book 18, Hadith 11
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 2, Book 20, Hadith 196