بُلُوغُ الْمَرَامِ
Bulugh al-Maram 236
The Book of Prayer
وَعَنْ أَبِي هُرَيْرَةَ - رضى الله عنه - قَالَ : قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ إِذَا صَلَّى أَحَدُكُمْ فَلْيَجْعَلْ تِلْقَاءَ وَجْهِهِ شَيْئًا , فَإِنْ لَمْ يَجِدْ فَلْيَنْصِبْ عَصًا , فَإِنْ لَمْ يَكُنْ فَلْيَخُطَّ خَطًّا , ثُمَّ لَا يَضُرُّهُ مَنْ مَرَّ بَيْنَ يَدَيْهِ } أَخْرَجَهُ أَحْمَدُ وَابْنُ مَاجَهْ , وَصَحَّحَهُ اِبْنُ حِبَّانَ , وَلَمْ يُصِبْ مَنْ زَعَمَ أَنَّهُ مُضْطَرِبٌ , بَلْ هُوَ حَسَنٌ . [1]
Narrated Abu Hurairah (RA): Allah's Messenger (ﷺ) said: "When one of you prays, he should put something in front of him, and if he cannot find something he should set up a stick; but if he has no stick with him he should draw a line, then what passes in front of him will not harm him." [Reported by Ahmad and Ibn Majah. And Ibn Hibban graded it Sahih (authentic). And he who claims it is Mudtarib (inconclusive) is not correct. Rather is Hasan (good)].
Sunnah.com reference: Book 2, Hadith 103