The Prophet ﷺ said: When one of you prays, he should put something in front of his face, and if he can find nothing , he should set up his staff; but if he has no staff, he should draw a line; then what passes in front of him will not harm him.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ إِذَا صَلَّى أَحَدُكُمْ فَلْيَجْعَلْ تِلْقَاءَ وَجْهِهِ شَيْئًا فَإِنْ لَمْ يَجِدْ فَلْيَنْصِبْ عَصًا فَإِنْ لَمْ يَكُنْ مَعَهُ عَصًا فَلْيَخْطُطْ خَطًّا ثُمَّ لاَ يَضُرُّهُ مَا مَرَّ أَمَامَهُ  

The Prophet ﷺ said: ...... He then narrated the tradition about drawing the line. Sufyan said: We did not find anything by which we could reinforce this tradition, and this has been narrated only through this chain. He ('Ali b. al-Madini, a narrator) said: I said to Sufyan: There is a difference of opinion of the name (Abu Muhammad b. 'Amr). He pondered for a moment and then said: I do not remember except Abu Muhammad b. 'Amr Sufyan said: A man had come to Kufah after the death of Isma'il b. Umayyah ; he was seeking Abu Muhammad until he found him. He asked him (about this tradition) but he became confused. Abu Dawud said: I heard Ahmad b. Hanbal who was questioned many times how the line should be drawn. He replied: In this way. horizontally like crescent. Abu Dawud said: I heard Musaddad say: Ibn Dawud said: The line should be drawn perpendicularly. Abu Dawud said: I heard Ahmad b. Hanbal describing many times how the line should be drawn. He said: In this way horizontally in the round semi-circular form like the crescent, that is (the line should be) a curve.  

عَنْ جَدِّهِ حُرَيْثٍ رَجُلٍ مِنْ بَنِي عُذْرَةَ عَنْ أَبِي هُرَيْرَةَ عَنْ أَبِي الْقَاسِمِ ﷺ قَالَ فَذَكَرَ حَدِيثَ الْخَطِّ قَالَ سُفْيَانُ لَمْ نَجِدْ شَيْئًا نَشُدُّ بِهِ هَذَا الْحَدِيثَ وَلَمْ يَجِئْ إِلاَّ مِنْ هَذَا الْوَجْهِ قَالَ قُلْتُ لِسُفْيَانَ إِنَّهُمْ يَخْتَلِفُونُ فِيهِ فَتَفَكَّرَ سَاعَةً ثُمَّ قَالَ مَا أَحْفَظُ إِلاَّ أَبَا مُحَمَّدِ بْنَ عَمْرٍو قَالَ سُفْيَانُ قَدِمَ هَا هُنَا رَجُلٌ بَعْدَ مَا مَاتَ إِسْمَاعِيلُ بْنُ أُمَيَّةَ فَطَلَبَ هَذَا الشَّيْخَ أَبَا مُحَمَّدٍ حَتَّى وَجَدَهُ فَسَأَلَهُ عَنْهُ فَخَلَطَ عَلَيْهِ  

I saw Sharik who led us in the 'Asr prayer during a funeral ceremony. He placed his cap in front of him, that is, for saying the obligatory prayer the time of which had come.  

رَأَيْتُ شَرِيكًا صَلَّى بِنَا فِي جَنَازَةٍ الْعَصْرَ فَوَضَعَ قَلَنْسُوَتَهُ بَيْنَ يَدَيْهِ يَعْنِي فِي فَرِيضَةٍ حَضَرَتْ