It is narrated from Sayyiduna Thawban (may Allah be pleased with him) that he (peace and blessings be upon him) attended a funeral. A mount was brought for him (peace and blessings be upon him), but he (peace and blessings be upon him) declined to ride it. When he (peace and blessings be upon him) had finished with the funeral and was leaving, a mount was brought to him (peace and blessings be upon him) and he (peace and blessings be upon him) rode it. He (peace and blessings be upon him) was asked about this, and he (peace and blessings be upon him) said: "The angels were walking on foot, and I did not think it fitting to ride while they were walking. When they left, or he said: when they ascended, I rode."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6854