The Messenger of Allah ﷺ saw a man walking among the graves wearing sandals, so he said, "You there, wearing the leather sandals, take them off."
حدثنا وكيع حدثني أسود بن شيبان عن خالد بن سمير عن بشير بن نهيك
أن رسول الله ﷺ رأى رجلا يمشي في نعلين بين القبور فقال يا صاحب السبتيتين ألقهما
Its isnad is sahih. Khalid bin Samir, also said to be Shumair, is trustworthy and his hadith appears in the Sunan works and in Bukhari's Al-Adab. Bashir bin Nuhayk is trustworthy, frequently cited, and his hadith is found in the works of the whole group. Hakim graded the hadith sahih (1/373) and said, "Sahih, though the two of them (Bukhari and Muslim) did not include it because the companion is not well known." Dhahabi agreed with him. A similar version was narrated by Abu Dawud (3/214, no. 3230), Nasai (4/96), and Ibn Majah (1/499, no. 1567), all of them in the chapters on funerals, on removing sandals in graves.