Hadith: If anyone of you is praying behind something that conceals him from people and somebody tries to pass in front of him, he should push him away; if he refuses, the praying person should use force against him for he is a devil

عًن أَبِي سَعِيدٍ رضي الله عنه قَالَ: سَمِعْتُ رَسُولَ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ يَقُولُ:

«إِذَا صَلَّى أَحَدُكُمْ إِلَى شَيْءٍ يَسْتُرُهُ مِنَ النَّاسِ، فَأَرَادَ أَحَدٌ أَنْ يَجْتَازَ بَيْنَ يَدَيْهِ، فَلْيَدْفَعْ فِي نَحْرِهِ فَإِنْ أَبَى فَلْيُقَاتِلْهُ، فَإِنَّمَا هُوَ شَيْطَانٌ».
[صحيح] - [متفق عليه]

Abu Sa‘īd al-Khudri (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: "If anyone of you is praying behind something that conceals him from people and somebody tries to pass in front of him, he should push him away; if he refuses, the praying person should use force against him for he is a devil." Another narration reads: "If anyone of you is praying, he should not let anyone pass in front of him; if he refuses then use force, for he has a (devil) companion with him."
Sahih/Authentic. - [Muslim]

Explanation

Before a Muslim starts praying, he can place something in front of him to conceal him from people so that the reward of his prayer is not reduced by their passing in front of him. When he starts communication with his Lord, he should lightly repel anyone who wishes to pass in front of him. If that person is not repelled with ease, this means he has violated the limits and become an aggressor. In this case, it is permissible to push him away and stop his aggression by force. Passing in front of the praying person belongs to the deeds of the devils who wish to spoil people's acts of worship and confuse them during their prayer.