Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1007
Musa b. Talha reported on the authority of his father: We used to say prayer and the animals moved in front of us. We mentioned it to the Messenger of Allah (may peace be upon him) and he said: If anything equal to the back of a saddle is in front of you, then what walks in front, no harm would come to him. Ibn Numair said: No harm would come whosoever walks in front.