Mukhtasar Muslim

Sayyiduna Talha bin Ubaidullah (may Allah be pleased with him) says: We used to pray and animals would pass in front of us, so we mentioned this to the Messenger of Allah (peace and blessings be upon him). He (peace be upon him) said: If there is something in front of you equal to the back part of a saddle, then the passing of anything in front does not cause any harm.