Sahih Bukhari Volume 4, Book 59, Hadith 3275

حَدَّثَنَا أَبُو مَعْمَرٍ، حَدَّثَنَا عَبْدُ الْوَارِثِ، حَدَّثَنَا يُونُسُ، عَنْ حُمَيْدِ بْنِ هِلاَلٍ، عَنْ أَبِي صَالِحٍ، عَنْ أَبِي سَعِيدٍ، قَالَ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ إِذَا مَرَّ بَيْنَ يَدَىْ أَحَدِكُمْ شَىْءٌ وَهُوَ يُصَلِّي فَلْيَمْنَعْهُ، فَإِنْ أَبَى فَلْيَمْنَعْهُ، فَإِنْ أَبَى فَلْيُقَاتِلْهُ، فَإِنَّمَا هُوَ شَيْطَانٌ ‏"‏‏

Narrated By Abu Said Al-Khudri : The Prophet said, "If while you are praying, somebody intends to pass in front of you, prevent him; and should he insist, prevent him again; and if he insists again, fight with him (i.e. prevent him violently e.g. pushing him violently), because such a person is (like) a devil."