Sahih Bukhari
Characteristics of Prayer
Volume: 001 / Book Number: 012 / Hadith Number: 827
Narrated 'Abdullah bin Abi Qatada Al-Ansari:
My father said, "Allah's Apostle said, "Whenever I stand for prayer, I want to prolong it but on hearing the cries of a child, I would shorten it as I dislike to put its mother in trouble."