Sahih Bukhari Volume 002, Book 020, Hadith Number 186.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 20. Shortening The Prayers (At-Taqseer)
Narated By Ibn AbbasÂ : The Prophet once stayed for nineteen days and prayed shortened prayers. So when we travel led (and stayed) for nineteen days, we used to shorten the prayer but if we travelled (and stayed) for a longer period we used to offer the full prayer.