Sahih Muslim
The Book of Prayers (Kitab Al-Salat)
Book Number: 004 / Hadith Number: 1006
Musa b. Talha reported it on the authority of his father: The Messenger of Allah (may peace be upon him) said: When one of you places in front of him so me. thing such as the back of a saddle, he should pray without caring who passes on the other side of it.