Musnad Ahmad 27:1136

Muhammad ibn Isma'il ibn Abi Fudayk narrated to us, al-Dahhak ibn 'Uthman narrated to us, from Sadaqah ibn Yasar, from 'Abdullah ibn 'Umar, that the Messenger of Allah (may Allah bless him and grant him peace) said: "When one of you is praying, let him not allow anyone to pass in front of him. If he refuses, let him fight him, for the companion (qarin) is with him."