Buraydah (radiallahu anhu) says, "Najaashi sent two simple black coloured socks as a gift to Sayyidina Rasulullah sallallahu alaihe wasallam. He wore these and made mash over them after performing wudu". (RU)
English reference (RU): Book 9, Hadith 69 (RU)
Arabic reference (RU): Book 10, Hadith 73 (RU)