«إذا وضع أحدكم بين يديه مثل مؤخرة الرحل فليصل ولا يبال من مر وراء ذلك»
The Prophet (peace and blessings be upon him) said:
"When one of you places in front of him (for prayer) something the size of the back post of a camel saddle (as a sutrah), let him pray and not mind who passes beyond that (sutrah)."
Hadith Referenceصحیح الجامع الصغیر / حرف الألف / 827