Hadith 503720
Chapter 9: Shortening the Prayer - كتاب قصر الصلاة فى السفر
وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ عَلِيَّ بْنَ أَبِي طَالِبٍ، قَالَ لاَ يَقْطَعُ الصَّلاَةَ شَىْءٌ مِمَّا يَمُرُّ بَيْنَ يَدَىِ الْمُصَلِّي .
Yahya related to me from Malik that he had heard that Ali ibn Abi Talib said, "Things that pass in front of a man praying do not break his prayer."
Reference Muwatta Malik 503720
USC-MSA web (English) reference : Book 9, Hadith 43