Humayd bin Hilal al-Adawi narrates: I was told by someone who heard a Bedouin saying: I saw the Prophet (peace and blessings be upon him) while he was praying, wearing sandals of cowhide. He spat to his left and then rubbed the place where he had spat with his sandal.
Ahmad recorded it; its chain contains a narrator whose name is not mentioned, and the remaining narrators of this narration are thiqat (trustworthy).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2242