From ibn Umar the Prophet, Sallallahu alayhi wa sallam, said, “When one of you is praying then do not let anyone pass in front of him, and if he refuses then fight him for indeed he has a companion [i.e. a shaytaan] with him.”
[Ahmad, Muslim and ibn Maajah].

From Abu Sa’eed who said: I heard the Messenger of Allah, Sallallahu alayhi wa sallam, saying, “When one of you prays towards something that acts as a Sutrah for him from the rest of the people and someone wishes to pass in from of him [i.e. between him and the sutrah] then push him back, and if he refuses then fight him for he is a Shaytaan.”
[Tirmidhi and ibn Maajah].

[Note: A Sutrah is an object placed in front of the one who is praying such that the people become aware that he is praying and do not pass directly in front of him but rather from beyond the Sutrah.]

His saying [no.1], “When one of you is praying then do not…” this is a general statement that finds specification in the hadeeth of Abu Sa`eed [no. 2], “When one of you prays towards something that acts as a Sutrah for him,” it is not permissible to push back or fight except for the one with a Sutrah.