It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that Abu al-Qasim (peace and blessings be upon him) said: When any one of you intends to pray, he should place something in front of him (as a sutrah). If he does not find anything, he should set up a staff, and if there is not even a staff, then he should draw a line. After that, whatever passes in front of him, it does not matter.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7392
Hadith Gradingحکم دارالسلام:إسناده ضعيف لاضطرابه وجهالة راويه أبي محمد بن عمرو.