It is narrated from a Bedouin companion (may Allah be pleased with him) that I once saw the Prophet (peace and blessings be upon him) performing prayer, and he was wearing shoes made of cowhide. Then he (peace and blessings be upon him) spat to the left side and rubbed that spot with his shoe.
Hadith Referenceمسند احمد / أول مسند البصريين / 20057
Hadith Gradingحکم دارالسلام:حسن لغيره دون قوله: من بقرة، وهذا إسناد ضعيف لإبهام الرواي عن الأعرابي