he was praying and a son a Marwan wanted to pass in front of him. He tried to stop him but he did not go back, so he hit him. The boy went the boy went out crying and went to Marwan and told him (what had happened). Marwan said to Abu Sa'eed: "Why did you hit your brother's son?" He said: "I did not hit him, rater I hit the Saitan. I heard the Messenger of Allah say: 'If one of you is praying and someone wants to pass in front of him, let him troy to stop him as much as he can, and if he persists then let him fight him, for he is a devil.  

أَنَّهُ كَانَ يُصَلِّي فَإِذَا بِابْنٍ لِمَرْوَانَ يَمُرُّ بَيْنَ يَدَيْهِ فَدَرَأَهُ فَلَمْ يَرْجِعْ فَضَرَبَهُ فَخَرَجَ الْغُلاَمُ يَبْكِي حَتَّى أَتَى مَرْوَانَ فَأَخْبَرَهُ فَقَالَ مَرْوَانُ لأَبِي سَعِيدٍ لِمَ ضَرَبْتَ ابْنَ أَخِيكَ قَالَ مَا ضَرَبْتُهُ إِنَّمَا ضَرَبْتُ الشَّيْطَانَ سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ إِذَا كَانَ أَحَدُكُمْ فِي صَلاَةٍ فَأَرَادَ إِنْسَانٌ يَمُرُّ بَيْنَ يَدَيْهِ فَيَدْرَؤُهُ مَا اسْتَطَاعَ فَإِنْ أَبَى فَلْيُقَاتِلْهُ فَإِنَّهُ شَيْطَانٌ